From the list of ingredients, and the fact that he is doing well on it, I would keep him on it. Do muscle testing eventually, but there isn’t anything that should interfere.
I wouldn’t want you to do anything with him cold turkey. Muscle test for what he is on and if they test OK and you have noticed results, then keep him on them. It is hard for me to say for sure because I don’t know what he has been on, for how long, and what changes have occurred. All of this is important.