Emaciated Mouse....please help!?

okay, at the pet shop i work at, There is 1 mouse cage..that is a 15 gal. tank. Its has OVER 40 mice. I took about 25 of them for feeders, normaly i breed my own feeders, but i know the lady personaly who owns the pet shop, and she was begging me to take some rats and mice...i took 6 rats out of about 60, and 25 mice of i would have to say 80 minimum (you cna bearly see the shavings on the bottom) The rats and mice are skin and bones! The rats even smell dead. They badly dehydrated. Especaly the babies, they couldnt reach the waterer. The baby mices poops are tar like. Ive got them in a separate room off my room, separated from my main group of mice. I gave both the rats and mice, hay, homemade rat/mouse mix, cat food/puppy chow, some wet cat food mixed with bread, and a tablespoon of oj. ...What can i give them to gain weight? How do i get the smell on them to go away...they really smell like dead/mixed with poop and pee. Ill be taking another group of mice and rats, in 4 days from the pet shop. Thanks