Im flabbergasted that they told you to replace your water with RO and not mineralize it. Bad LFS, bad. No, adding RO will not solve your issues, but replacing the water with properly mineralized RO may help.
First step is to get a better test kit, drops from either API or Seachem. A hand held pH meter is also extremely useful.
You’ll also want a TDS meter if you want to use RO and mineralize it. For minerals: Salty Shrimp OR Shrimp King Shrimp Salt.
And yeah reading the comments… Not sure which store sold u stratum but thats not beginner friendly, it will change your water parameters as you have seen
Not all neos can survive in low pH. There are breeders with neos adapted to stratum so you need to buy from them. If you get neos grown in alkaline water (which is most common) then they will die in acidic waters
Rosiepuff 
Im flabbergasted that they told you to replace your water with RO and not mineralize it. Bad LFS, bad. No, adding RO will not solve your issues, but replacing the water with properly mineralized RO may help.
First step is to get a better test kit, drops from either API or Seachem. A hand held pH meter is also extremely useful.
You’ll also want a TDS meter if you want to use RO and mineralize it. For minerals: Salty Shrimp OR Shrimp King Shrimp Salt.
What substrate do you have in your tank?
Ive shared this guide in the sub, but in case you haven’t run into it: https://docs.google.com/document/d/10Fc-gVpIc8UZe1qn0bkXluO-zpBtz0IiSDFFr_7FBnA/
This all sounds like active substrate
And yeah reading the comments… Not sure which store sold u stratum but thats not beginner friendly, it will change your water parameters as you have seen
Not all neos can survive in low pH. There are breeders with neos adapted to stratum so you need to buy from them. If you get neos grown in alkaline water (which is most common) then they will die in acidic waters