I had 4 glofish in 10 gallons tank waiting to go into the main tank but one was already sick and died. No signs of skin disease or anything. Down to three fish. One big sized fish and two baby ones (small sizes) in there now and everything was fine until I got home and I noticed big one have his tail severe nipped? His tail was fine this morning. Help?? Two another ones are really small, much smaller than the big one..