A couple things...
1. Try to lower the tamp as Kymmie suggested.
2. What kind of filter do you have? RCS don't swim per se, but if there's too much current they will hide.
3. How long have you had the tank? MAKE SURE you cover your filter intake, since RCS only live about 1-2 years- breeding them is the only way to keep a constant supply, even if it's for your own entertainment.
4. PH isn't SO important, the original species was in soft water. Calcium is more important than PH, as long as Ph is within reason (preferably 6.0-8.0), what's the Kh? Do you put leaves in the tank? If the Kh (calcium content) is too low and/or you dont give them leaves, they will die when they try to molt.
Just go out in the woods and find a leafy tree (I prefer oak or maple) and soak the leaves in water until they turn blackish brown and sink, and drop them in. Makes nice decor as well. You can buy almond leaves on aquabid supercheap if you're worried, but I wouldn't do it with RCS. IMO, the risk is marginal. If I was breeding high-grade crystal reds, you better believe I'd be using almond leaves. With shrimp worth about 50 cents each? not so much.)
I no longer keep RCS- I sold out my tank with the agreement that my business partner would give me a discount to restock, and he hasn't responded to my emails at all.
That being said, he does still sell them. I don't plan on updating my topic because of that, but he does still sell them and they're good quality. I'll honor anyone who posts there trying to buy.
Now my shrimp tank is a Guppy maternity ward and grow-out tank. (It's SUPER heavily planted).
I made the mistake of selling some guppy females, so now I only have 4 females to 12 males... I'm keeping the females seperate fo they don't get pestered to death, and letting their fry grow up with them. quite touching to see them eat together, and the females leave them alone when they come out for feeding time. The mothers haven't eaten any young, I think they're treating it as a retirement home. Just laying around, but they're healthy.