Comb color can vary for a lot of reasons, hormones, stress, excitement, etc. I bird that was anemic from mites or lice would likely be pale all the time. This has lots of pictures to help with ID of whether you have a problem with either of them:
https://the-chicken-chick.com/poultry-lice-and-mites-identification/
Some mites live in the coop and only come out at night to feed on the birds, so checking after dark with a headlamp or flashlight is necessary. If you find you do need to treat then a product containing permethrin is most common. DE is honestly a waste of money, it doesn't work and it can cause respiratory irritation. Elector PSP is also good, but much more expensive than permethrin. You will need to treat the birds, and clean out and treat the coop also, removing all bedding and nesting material and replacing with new after treatment. For mites particularly you will need to do at least 3 times usually at weekly intervals to get those that continue to hatch.