My Son's Doctor Who I Trust Implicitly Has Prescribed A

My son's Doctor who I trust implicitly has prescribed a low dose of propranolol and has added Zoloft. Both for anxiety. He was nauseous yesterday before taking both together along with arythramiazin all at once. He threw up about 2 hours after taking the pills and felt much better. Today he woke up feeling nauseous and is not feeling better yet. He may have a bug, but I am wondering about the taking of these two meds together. Any help would be appreciated.