for sure thats way too many feeders, if you want to give them feeders get a 10 gal containment tank and buy 50 or so to put in there, then over time feed them a few at a time. you should never add more than 3 fish at a time. rosy reds or other feeders you can get away with more but not 48. that is more than likely your prob. prob like TwistedPenguin said and a bacterial bloom. feeding them raw shrimp or silversides instead, plus its alot easier on the wallet than feeders, less chance for disease, just plain healthier, and could possibly stop the bacterial bloom. if they dont eat it the first day dont get discouraged, just net it back out and throw it away. then try again the next day. they will eat it before they starve to death. just make sure you take the shell off the shrimp. this is turning into a book so ill stop now.