I have three pygmy cories that I've bought in the last week. The last couple days I have noticed that at least a couple of them (not sure if it's all three, two of them are hard to tell apart) are flashing a little. I've never seen this before (at first I thought it was a funny idiosyncrasy until I Googled it). My other fish seem normal. I see no other external signs of a problem, and the cories are acting fine (as far as I know, obviously my experience with them is limited). I read that a pH change can cause flashing; my pH is steady at 8.2, but the LFS pH might be lower if they use RO water. Ammonia, nitrates, and nitrites are 0. Should I treat for something like skin flukes just in case? No experience with this at all.