Does a rabbits teats change in appearance?

Yes. A mothers teats will become larger as soon as she nurses til the babies stop nursing and then her teats will get smaller as her milk drys up.

If they become really large, hard and have a fever your rabbit has mastitis. Best to get her to a vet. They will be very sore and she will not let babies nurse and could bite them. If gone untreated the doe could lose that teat. (not a pretty sight.)