What gangster posted will help them get better nutrition. Bloodworms are kind of like fast food -- very tempting and tasty, and great for getting new fish settled, but not so hot when it comes to nutrients. You don't want to feed them long term.
He is still awfully skinny, though. If he is EATING and still skinny, ALSO treat for parasitic worms in addition to giving them better food. A good anti-helminth drug is praziquatnel (generic name). PraziPro is an example of a brandname for the drug, and follow manufacturer instructions. You may need to isolate the skinny guys so their food doesn't get gobbled up by the healthier ones.