I got 5 kelberis about 1 month ago. 1 died after a week and the other just about a week ago. The first one was too skinny and did not really got very far. The second one was actually one of the biggest in the group but suddenly got weak and was gasping a lot then started pooping white strings. The 3 left are with 3 Azul of the same size and 5 datnoids. The Azul and datnoids are not gasping for air but all 3 kelberis are just struggling and now having white string poop. They don't have sunken belly so they must be eating but the white poop and struggling for breath bothers me. . I don't see any aggression other than datnoids among themselves. I have air stone in the tank. Water change 20% every other day, 55 gal tank. Should I start medicating the kelberis? what's the recommended medicine? I noticed the gasping of all the kelberis about a few days before the last one died.