this happened to me too! They used to love pellets, thats what they were fed at the pet store and it was what they were used too. I changed them to heart which at the time i thought was an ok staple, which they go crazy for, and now they will not go back to pellets, they just spit them out! They're not good enough any more
(they are on worms now)
they'l spit them, then happily eat a worm instead. I think they get picky when they know tastier options are out there. Its like a kid that doesn't want to eat vegetables... the more healthy but less tasty option.
No offense to anyone here, but the general oppinion of your axolotl MUST have pellets/worms as the staple of their diet i think is blown a little out of proportion. It is ok to feed him only bloodworm for a little while, he will still thrive and be healthy. He is not going to drop dead. After all they would not have only eaten only one thing constantly in the wild, even if it was the most nutritionally complete.
its like you will not be diseased if you eat only potatoes, you could actually survive quite well on them...you'd just not be AS healthy as if you ate a more balanced diet. Many healthy axolotls live happily on blood worms and beef heart, even if they are not the full package diet recomended on the forum. Mine lived fantastically on heart for a few months (they even bred a few times) while i was sourcing worms.
i'm not sure on the exact nutritional value of bloodworms, so you might have to keep in mind the moderation of feeding... eg. I fed my axies once or twice a week on the heart because it has a much higher than recommended fat content. I think each food would have a different feeding value.
i'm not saying its the best food for your axies to be on long term, but your axies will still be OK on bloodworm. I have yet to see an axolotl turn down an earthworm, so if they are spitting pellets maybe look for some of them in the meantime?
also i think its sort of cute when they spit things out or vomit... is that wierd?