I would suggest you are experiencing the same aches and pains of any artist. The best thing is to eat well (the supplements you mention will not help) get plenty or rest and build into this new career gradually. Overtime you will naturally strengthen much like someone who taken up climbing for the first time. Their arms are dead after about 5 minutes. On that note, and being that you are in LA, I would recommend finding a wall climbing gym and maybe doing a bit of climbing once or twice a week. This will give you incredible upper body strenght and endurance.

Best of luck