Yes... you should have completely broken down the tank before putting red eyes in there... Replaced all the substrate and washed all the pants again. Bbased on the super fast death rate.. have you investigated the water quality? Also are you keeping the vivarium at 65-85 percent humidity. (Do you handle your red eyes without washing your hands) Those (besides disease already carried) Will kill your frog the fastest. Photos would be greatly appreciated.

-Corey