Yeah he just might be very weak right now is all, not actually sick, just weak. It's the same as if you were to eat maybe half a meal a day and then continue to walk around/run all day long; you'd be feeling pretty weak too!
For now, if you can, feed him twice a day but work your way up to it so you can do like 1 pellet in the morning and one at night for a few day's so that it doesn't completely shock him. This way with the two feedings, he's not going a full 24 hours without food which will immediately start to give him more strength and energy. Then after a few day's up it to 2 in the morning-ish time and then 2 at night and eventually you can go back to one feeding a day if you like around 6-8 pellets a day should be fine. But you feed whatever you feel he needs. Sometimes if I feel like my boy's are looking particularly skinny, I'll give them up to 10 pellets of NLS but usually 6-8 is a good number for once a day.
Again if you wanted to split that you can do 3-4 in the morning and 3-4 at night and that will be just fine! Bloodworms can be feed twice a week, you can do like pellet feeding in the morning (3-4 when he's good for it) and then 3-4 bloodworms at night or whatever he wants to eat. I believe they say "feed as much as your fish will consume in 30 seconds" so one at a time, I use tweezers to feed them and usually they can gobble down anywhere up to 5-7 bloodworms but I'd usually fast them the day after that so I tend to feed them Saturday/Sunday and my usual fasting day's are Monday and Tuesday since I can't be at that house those day's as I'm elsewhere.
At least now you know what to look for in foods, it will make buying them easier and you'll be very efficient at it ^_^ I know it's never fun finding out that the stuff you just bought isn't very good though, I've had my fair share of buying foods I thought were good only to find out they weren't. I have like 4-6 other flake/pellet/BW foods in my fish drawer right now not in use lol. It's all part of learning though, but yes it sucks.