I think somehow you misunderstood Brian, because I think that has to do with shedding, not feeding.
How big are their tubs and what do you have your tub layout like? What are your exact temperatures and humidity?
What time of day are you feeding? Are the tubs in a quiet area during feeding, or are you trying to watch them during the feeding process?
These may sound like dumb questions, because it does seem like you have a good amount of knowledge already, but all of this could narrow down something you could have missed.
The temps in the back read about 92 and the front sites about 77 degrees. The water dish sits in the front right or left corner depending on the sex. I don't have anything that reads humidity but there is condensation in the front fo about a 3-4 day period and then i spray the front agian.
I am always feeding in early evening, it is defenitly a quite area because its in the basement away. Now i have been trying to feed the females outside of their tubs so that the rats don't get bedding on them, that could be the issue.