If he is still eating hay then I personally wouldn’t be too concerned. You can keep an eye out for any behavioural changes and perhaps switch to daily weighing for a while to make sure there is nothing else going on, but as I said I wouldn’t be too concerned as he is still eating his hay.
Have you tried him with herbs, my boys can’t resist a herb even when they were ill. As for carrots, they should only be fed once or twice a week as they have a high sugar content.
My only worry would be the nutritional value vegetables add to the diet, but off the top of my head if he was still eating his hay and getting his 1tbsp of pellets a day plus his romaine lettuce, this shouldn’t pose too much of an issue. Perhaps if this continues for say a couple weeks you could give your vet a phone and ask them if they think this would pose any issue for your boy, as they will certainly have a better understanding of nutritional values than me.