Shrimp are sick and dead in an established tank
I have a 60 gal heavily planted tank, which is been running for more than an year. With a growing colony of RCS, neon tetras and a couple of kuhli loaches they all were doing great. As I was busy for last couple of weeks , I couldnt pay much attention to it. Today while carrying out usual maintenance, I couldn't find any RCS in it, which usually roam around everywhere. Upon a close inspection, I could only find one of them, which is sick and not reacting to my hand, usually they run and hide. There were atleast 30 of them, and I am sure that, with plenty of space to hide from neon tetras and kuhli loach ignores my RCS, predation is not an issue. But, had seen an explosion in population of snails, I am aware of calcium imbalance caused by it, but I doubt whether it can kill 30 RCS in a period of 3 weeks. Any guess what happened to RCS and any inputs on what should I do before introducing some more RCS. ?