Hi!
Please step in with support feeding as soon as your boy has lost 2 oz very quickly or 3 oz over more than a week.
Hay makes about 80% of the daily food intake, your piggy can lose a lot of weight without you noticing when you just fix on the ca. 15% of veg he has lost interest in - that is like worrying about your piggy not wanting his afternoon ice cream without checking on whether he is eating breakfast, lunch and dinner. Only the scales (normal cheap kitchen scales from the store will do) can tell you the real amount of weight loss and how much you need to support feed.
You can mush up pellets in a pinch. Our comprehensive emergency and bridging care advice contains all the necessary information and practical tips for the exactly the situation you are finding yourself in to keep your piggy going until he can see a vet and until any medication is kicking in. Loss of appetite is a very wide field; it can be dental but it can also be a whole lot else. Only a hands-on vet examination can tell.
Here is the link. Please bookmark, read and use it:
Emergency, Crisis and Bridging Care until a Vet Appointment
All the best! I hope that your vet can find what is the matter.