It could be a lot of things.
At 77F your shrimps’ lifespan will be accelerated, but if they are trying to climb out that is a big red flag.
You mentioned concerns about your water being too hard, what is the KH and GH? Any idea of the TDS?
Did you recently add any new plants, decorations, or start new supplements?
Your nitrates were a little high, cherries like between 0-20ppm, try to keep the number consistent instead of waiting for 0 then spiking it to 30.
Could also be co2. Warmer water doesn’t hold co2 as well and the drop checker is a lagging indicator, so it’s possible they are just getting low on oxygen when the lights go off? Are you getting pearling from your plants during the day? That would indicate oxygen saturation.
The water change itself is a likely culprit. Shrimp do not do well with sudden environmental changes. Most people will limit their water changes to 10% or less a week because of that. Some even add the new water very slowly to acclimatize the shrimp to the water change. It kind of depends on your water chemistry, the biological activity of your tank, and how frequently you do water changes.
Imo, these are good water parameters for cherry shrimp:
update: lost another shrimp today… no co2, topping off only with RO/DI water, water parameters are stable, etc etc…
starting to doubt the integrity of the shrimps i’m buying honestly!!
this one that passed away was very translucent when i bought it, almost looked like a blue jelly. also had a red-ish spot, that i chalked up to other matters before.
wondering now if those were red flags for its health…?
kaylekhan 
It could be a lot of things.
At 77F your shrimps’ lifespan will be accelerated, but if they are trying to climb out that is a big red flag.
You mentioned concerns about your water being too hard, what is the KH and GH? Any idea of the TDS?
Did you recently add any new plants, decorations, or start new supplements?
Your nitrates were a little high, cherries like between 0-20ppm, try to keep the number consistent instead of waiting for 0 then spiking it to 30.
Could also be co2. Warmer water doesn’t hold co2 as well and the drop checker is a lagging indicator, so it’s possible they are just getting low on oxygen when the lights go off? Are you getting pearling from your plants during the day? That would indicate oxygen saturation.
The water change itself is a likely culprit. Shrimp do not do well with sudden environmental changes. Most people will limit their water changes to 10% or less a week because of that. Some even add the new water very slowly to acclimatize the shrimp to the water change. It kind of depends on your water chemistry, the biological activity of your tank, and how frequently you do water changes.
Imo, these are good water parameters for cherry shrimp:
PH 6.5-7.5
GH 6-8
KH 1-4
TDS 150-250 change water over 250
Temp 21-24c 69.8-75.2
I’d stop the co2. Make sure it’s not an oxygen problem bc if they’re climbing up, my instinct would be “they can’t breathe”
got some pics of the one struggling, who fell down and seems stuck…? moved it so it’s upright and can do what it needs to do hopefully
is it failing to molt due to hard water?
https://preview.redd.it/ap2umoat48nc1.jpeg?width=4032&format=pjpg&auto=webp&s=213da23b496eeb8b99455a72e0b7bac58514c318
shrimp died 🥲
https://preview.redd.it/hyeswgw9h8nc1.jpeg?width=3024&format=pjpg&auto=webp&s=8db20b0351b916dceae0b3c9a9c834eeb2da6fbb
Are you monitoring ammonia, nitrites and nitrates? How long did you run the tank before adding the shrimp?
Any updates OP?
update: lost another shrimp today… no co2, topping off only with RO/DI water, water parameters are stable, etc etc…
starting to doubt the integrity of the shrimps i’m buying honestly!!
this one that passed away was very translucent when i bought it, almost looked like a blue jelly. also had a red-ish spot, that i chalked up to other matters before.
wondering now if those were red flags for its health…?