Try live blackworms if you can source them; my puffers seem to like them quite a bit. Did you treat your puffers with internal parasites? I've kept C. asellus quite a few times, and the ones that were treated for parasites adjusted to captivity a lot better than the ones that weren't. And I do agree with Deadeye; puffers are a lot more individualistic. One of my puffers will eat nothing but brine shrimp, one is an absolute glutton that eats nearly everything I offer, and one's picky about everything, but usually settles for a bloodworm or two. I think variety is key; offer as many unique foods as you can and see if they'll eat it. I tend to give mine small portions of boiled shrimp, frozen krill broken into chunks, occasionally blackworms if my LFS has some, frozen bloodworms, frozen brine shrimp, frozen mysis shrimp, small chopped earthworms, tiny bits of silverside, occasional ghost/neocaridina shrimp, and I have seen them eating some detrius worms and small aquatic copepods. They are in a community tank with some tetras, which do act more like a dither. How many puffers do you have? They seem to do a lot better the more there are; you also do have to be careful when purchasing puffers as I believe almost all are wild-caught, and they tend to stress out much more easily. Ones with inverted bellies, lopsided swimming, tendency to hover, tattered fins, etc. often have parasites and usually don't seem to react too well to treatment and captivity. Good luck! Hopefully they can get established onto something soon. It's good to see that at least one puffer's eating. He might encourage the others to eat as well.
