Tortoise not eating

[TessaRuth]

Hello. I have a twelve year old Horsefield. He is a good weight and hibernated successfully this winter, coming out in mid-January. Since then, all has been well and his normal habit is to eat every day with perhaps a day off here or there. However, since four days' ago, he hasn't eaten at all. In all other respects, he appears healthy and is active and bright eyed. The inside of his mouth is pink and healthy-looking too. This lack of eating has not happened before and I'm wondering if I should be worrying and go to the vet. On the other hand, can this happen and be nothing to worry about? I have only had him for ten months so I'm not quite sure what is normal or not at the moment. I've given him several warm baths already.
Thank you so much for any help.