All three are males from the same litter (per the breeder), as I specifically requested only males. The reluctant eater unfortunately now also has not been interested in taking live fish either. I assume moving him into a separate place has been stressing him out. Because of that I've gotten him his own housing today so I can leave food in with him safely as he clearly is also stressed out by being observed. Hopefully he starts eating while alone and unobserved.

Not sure where to find croaker, but I've been offering nightcrawler pieces, scented pinky pieces, f/t silverside pieces, and once salmon pieces. One of the ones who is happily eating likes fish, the other likes worms. I am planning to try to get them eating pinky pieces, but it's not a priority. I have now found a place to get feeder guppies for the reluctant eater, so he has been offered those as well.

If you have any additional advice, I'd appreciate it. Right now I assume the best thing for him is just to be alone and be left alone except for placing in food, cleaning, and giving water, all of which I will disturb him as little as possible.