Parameters we cannot see here:
Ammonia, Co2 can both be cause of a death spike. There are Testing kits out there for this.
Parasites, Bacteria. Of you can see anything off about them physically or funny behaviour (walking backwards, in circels, not eating (you can see a dark strip across the back, which indicates they are full. Is that clear, they have not eaten!) etc)
Stress. Are They zooming about? This is a good indicator for the things above.
Heads up, hope this gets sorted out!
EDIT; i just saw the Co2 Diffuser, my bad!
Also 4 times is a bit much, be sure to clean out the Rest afterwards. Otherwise it can lead to pests and pollution!
What food are you adding to feed them? 20 japonica is a LOT and they’re ravenous hungry little guys. Your parameters look fine, as long as you drop acclimated them. Some loss is to be expected, especially among breeding age adults as adult shrimp are less adaptable than younger ones.
You need to be feeding them because this tank is too new and doesn’t have biofilm for them to graze on. Make sure whatever you’re feeding doesn’t have copper in it, as some bottom refer wafers for plecos and stuff do, and it’ll poison invertebrates.
So what I did that was killing my shrimp was doing my water changes too fast. I was a dummy and I just dumped the water in the tank once I treated it. Add it slowly over like 15 minutes so as not to stress or shock the little dudes too much
He tells me the water is absolutely fine and recommended to reverse the changes I did to see how it works out, so i stop feeding flakes and got the O2 diffusor out
Things that changed since friday: I got new plants and a Lava rock from a highly recommended Dutch webshop, I started adding some simple fish flakes as food and added the O2 diffuser and shrimp guards to the filter.
I am a 33yr old guy but kind of feel like a loser for letting my new buddies down, I really hope I can save them. The other guys are roaming around, are eating the food I give them and the babies are chilling on the spiderwood.
I just want to thank all who responded to this thread, I am a bit gutted over the losses but am so happy this community is super supportive. It is almost bedtime in the Netherlands, just tested my water again and the readings are same as this afternoon. Gave them some extra shrimpfood which most of them ate. Hopefully the buddies make it through the night…
I am starting to think about parasites of disease? But they seem so normal, the dead ones are colored a bit pink instead of grey is that a lead to something?
I started with five cherry shrimp a couple months ago. They had their babies, and I’m pretty sure they’ve all died(the parents). So I’m guessing lifecycle related.
Your tank is way too clean for shrimp, try neglecting it for a few months and they should thrive
Edit: while I was being snarky it’s serious advice I had a lot of random deaths and was constantly trying to make my shrimp tank perfect and “fix” it. After giving up and just letting my tank be, my shrimps start thriving. If you clean often and do water changes I would cut it in half. If you feed daily, cut that in half. Add some Cataappa leaves and start feeding BacterAE in small doses once or twice a week. Throw in a cuttlebone to maintain calcium levels and let them be. I stopped doing water changes months ago, I just top off evaporated and stopped cleaning altogether, I’ve never had more active shrimp and more babies – they love the neglect! It’s the environment they thrive in!
jaxzie 
Your KH looks way too high. That might cause problems with molting.
Get proper kits, and test your tap water. Gives us that info to help you further.
get an api master test kit and gh/kh test kit. strips aren’t accurate and you might find your answer there
Parameters we cannot see here:
Ammonia, Co2 can both be cause of a death spike. There are Testing kits out there for this.
Parasites, Bacteria. Of you can see anything off about them physically or funny behaviour (walking backwards, in circels, not eating (you can see a dark strip across the back, which indicates they are full. Is that clear, they have not eaten!) etc)
Stress. Are They zooming about? This is a good indicator for the things above.
Heads up, hope this gets sorted out!
EDIT; i just saw the Co2 Diffuser, my bad!
Also 4 times is a bit much, be sure to clean out the Rest afterwards. Otherwise it can lead to pests and pollution!
Oh and I do a 20 percent water change every week
What food are you adding to feed them? 20 japonica is a LOT and they’re ravenous hungry little guys. Your parameters look fine, as long as you drop acclimated them. Some loss is to be expected, especially among breeding age adults as adult shrimp are less adaptable than younger ones.
You need to be feeding them because this tank is too new and doesn’t have biofilm for them to graze on. Make sure whatever you’re feeding doesn’t have copper in it, as some bottom refer wafers for plecos and stuff do, and it’ll poison invertebrates.
So what I did that was killing my shrimp was doing my water changes too fast. I was a dummy and I just dumped the water in the tank once I treated it. Add it slowly over like 15 minutes so as not to stress or shock the little dudes too much
I got a test kit and tested with my neighbour who has a koi pond and is a PHD in microbiology, sera testkit shows:
Ammonia NH4: 0
Nitrate NO3: 0 – 10
Nitrite NO2: 0
Chlor: 0
KH: 6 KH
PH: 6.5 / 7
He tells me the water is absolutely fine and recommended to reverse the changes I did to see how it works out, so i stop feeding flakes and got the O2 diffusor out
Things that changed since friday: I got new plants and a Lava rock from a highly recommended Dutch webshop, I started adding some simple fish flakes as food and added the O2 diffuser and shrimp guards to the filter.
I am a 33yr old guy but kind of feel like a loser for letting my new buddies down, I really hope I can save them. The other guys are roaming around, are eating the food I give them and the babies are chilling on the spiderwood.
I just want to thank all who responded to this thread, I am a bit gutted over the losses but am so happy this community is super supportive. It is almost bedtime in the Netherlands, just tested my water again and the readings are same as this afternoon. Gave them some extra shrimpfood which most of them ate. Hopefully the buddies make it through the night…
I am starting to think about parasites of disease? But they seem so normal, the dead ones are colored a bit pink instead of grey is that a lead to something?
Strips aren’t accurate! Don’t trust them! Take some water to a LFS and they may be able to test it with an api test kit if you aren’t able to buy one
And like 4 of the remaining adults are berried at this moment
How long has ur tank been set up? Looks on the newish side to me.
RO water ? Tap water ? What’re you using to re mineralize
I started with five cherry shrimp a couple months ago. They had their babies, and I’m pretty sure they’ve all died(the parents). So I’m guessing lifecycle related.
Your tank is way too clean for shrimp, try neglecting it for a few months and they should thrive
Edit: while I was being snarky it’s serious advice I had a lot of random deaths and was constantly trying to make my shrimp tank perfect and “fix” it. After giving up and just letting my tank be, my shrimps start thriving. If you clean often and do water changes I would cut it in half. If you feed daily, cut that in half. Add some Cataappa leaves and start feeding BacterAE in small doses once or twice a week. Throw in a cuttlebone to maintain calcium levels and let them be. I stopped doing water changes months ago, I just top off evaporated and stopped cleaning altogether, I’ve never had more active shrimp and more babies – they love the neglect! It’s the environment they thrive in!