Just because your Fire Reds can molt in that water, it doesn't mean the CRS can. They do have different parameters and it's hard to find a common ground that makes both of them happy. If the CRS are older and don't molt often, I find they can take different water a bit better but as youngin's, they need more ideal water as they molt more often.
Also, probably shouldn't have done a water change after getting them only 2 days. They are stressed for about a week after changing water, being shipped, etc. I just 17 new yellow shrimp the other day, from 3 different sources. After acclimating them from 3 different waters to my tank, I put off this weeks water change so I don't stress them anymore. I got them Saturday and today is supposed to be water change day but I'll wait till next week as they are all going to be stressed from being packed up, moved around to my shrimp meet, sat there all day in a bag, ride home, acclimation to different water, if I changed today, I would probably have some dead ones.
*edit* got ninja's by raven. lol.
20g platy, , 2 x 10g shrimp, 3 x 20g shrimp, 7.5g shrimp and 1 great dane/mastiff puppy.
Sump Pimp #2
My Tanks and my shrimps