This is a tough spot for you. You have to relax, be patient, worry, and be careful all at the same time. It could be the new environment that he hasn't become acclimated to or the new tank mates that intimidate him. IMO you should keep feeding as you have and if he doesn't eat by the weekend you should put him in an isolation tank. Use water from the main tank to eliminate the stress of different water. Then try the same prepared foods that you are using to see if it was the environment or tank mates. If this works, you will have to fatten him up good before putting him back. Unfortunately this move will stress him out so he may not eat for a day because of the move itself. If this doesn't work I would try live before he gets too weak. There is nothing worse than watching a fish starve himself to death. Good Luck!