Hi there, welcome
I went ahead and inserted your photos, you had attached them, but not inserted them.
The scaly bits with red make me think it’s probably mites. I doubt it’s from the food, but sometimes buns can have mites and no symptoms, and stress can cause them to flair up. There are other possibilities too, like a fungal infection, but based off the location I think that’s less likely.
Your vet can diagnose for sure. A common treatment is Revolution (it has other names outside the US), which is a topical treatment that you apply monthly. Be sure to never use anything containing fipronil on rabbits.
As side note, I wouldn’t recommend those Kaytee pellets, or any pellet that has a mixture of different pellet types and seeds in them. They encourage selective eating, and usually don’t have the best ingredients for buns. Look for one that is timothy based (or alfalfa if bun is under a year), and has at least 18% fiber content.If you are currently using the Kaytee, you can pick out the grains and cereal bits and just feed the actual pellet part while you slowly transition. You should transition slowly over the course of a month.

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The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.