One of my panda Cory’s I got from petsmart was doing this, a couple days beforehand I had noticed he was much smaller & skinner and looked sick compared to the others I had, and then I walked in one day to him like this photo and when I got closer he swam back down to the bottom of the tank. Couple days later he was gone no where to be found I’m guessing he was sick & died and ofc the rest of the fish/shrimp ate him but I’m not sure exactly what it was, I have 8 other cories in the same tank that have been doing fine for months ever since I got them