I think I bought them infected with something.... Either parasites and/or fungus. Lost three within a week of purchase (one wouldn't eat and just wasted away with little or not other signs, one I found floating at the top of my tank completely white, and another (I would have to say the weakest of the six--had one eye) I just found dead at the bottom of the tank). I medicated the tank for internal/external parasites because the remaining three were constantly flashing and the larger one had white/gray film or fuzzy growth on the back end near the tail. That seemed to help, but after I stopped treatement, they started to flash again and the LFS owner suggested Tetra meds that treat everything since he had no idea what was causing their behavior or deaths. While that seemed to help, it damaged my biological filtration and my tank underwent a mini-cycle. After several water changes and monitoring everything, everything seemed fine--the cories have been eating well and very active. However, this past Sunday, I noticed that one of the smaller cories had what looked like small, white stringy growths here and there on his body. Since I read somewhere that Ich meds can treat other parasites and deseases, I dosed with the Ich meds I had on hand. While that seemed to help get rid of the growths, two of my three cories have been very lethargic. I know they are sensitive to certain meds and salt. I'm just at a lose as to how to get rid of this once and for all. I've had nothing but problems with them.