. It sounds like your husbandry is on point. Imo, I think the hot spot can come down about 5 or 6 degrees. What is your feeding schedule frequency? Third week not eating but how many feedings has he missed? Actually three weeks is not that long since you said he has had 3 feedings prior. Personally , I would wait another week to 10 days. Depending on what happens at that feeding I would go to plan b. Relax for now and monitor his weight.