Sorry for the delay in replying. You might consider posting on the parents forum. It's very active and, since you're posting about your son, you are likely to get other parents replying. I suspect a lot of the adults on the board don't feel qualified to comment which would explain the lack of quick replies.
Generally, in my experience, if my son was growing then he was in remission or at least partial remission. Lack of growth was a sign he was not in remission.
IF he's having other symptoms like fatigue, belly pain, diarrhea or constipation, bloody stools then I would be concerned that he's starting to flare.
If he's losing weight then I would definitely be worried and contact his GI.
It's also possible that he's depressed and isn't eating for that reason. A lot of kids with IBD get depressed at some point and may benefit from some therapy or medication.
I've never heard of remicade causing a lack of appetite.
