I have had 14 skirt tetras for 6+ weeks. Some are bigger than others but they are all plump and growing except one. I hadn't really noticed one of the glofish tetras hasn't seemed to grow at all and seems a little skinny. There are no other signs of disease. He does eat but not much at a time. I tried catching him to put him in the qt tank but he can still swim very fast. I didn't want to stress him or the other fish so I've given up for now. They are in a 75 g tank and it is cycled, 0,0,10 with pH around 7.5 and temp 78. I'm thinking it could be genetic since I'm guessing glofish probably have a limited gene pool but want to rule out any other disease (TB, parasites, etc).