Feeding problems

[200xth]

I am feeding frozen rats yes. She was eating fine before and now its been 3 weeks and she went from 1085grams (since she last ate) to now 1038grams (since she refused). Im worried because she spends all her time on the cold side and she goes to strike but doesn't its weird. And yes they are different colours some white and some black. but she has eaten one of each before so i thought she liked both colours as well i didn't think it mattered in a way. Although i do know sometimes they are picky that way. My process is I defrost, heat it with really warm water and zap the brain with a hair dryer and offer it

Try a live rat.

EDIT:
Also, what size rat is it (grams)? What time of day are you feeding? I have one finicky eater who will only eat after I turn off all the lights and go to bed.