Is there anything new in the house? Believe it or not, anything can stress a bunny out, and sometimes this is what happens. Also, If your bun is being fed unlimited pellets, then they wont be interested in anything else. My buns are almost 5 months and are supposed to be eating unlimited pellets but they are hardly touching their hay so I now limit them to 1/3 – 1/2 cup of pellets and a cup of greens, which they are being slowly introduced too. This too can cause problems. If you try to introduce a new green or veggie to their diet to fast, they will get ill and not feel well. I start out by using the greens as a treat during clicker training, or at the end of the day treat. Another thing would be to check your food. If it has been over 6 weeks with the same bag of food, buns will lose interest, and if the hay isn’t at least decently fresh, they will deny it. If you feed your bun fruits, like berries, or bananas, be sure not to give them too much, as this will upset their digestive system. I give one berry to a bun, and they usually stop half way through it so I give the rest to the other. Very small amounts of fruit are better.
When a bun is sick, they usually have a different attitude. They can become aggressive, or scared, or just act “blah”. If they are acting different, I suggesting finding a bunny vet. If they are acting the same, take the past information into consideration. I hope this helps!