Do I have picky eaters?!

I own two green spotted puffers, they’re both juveniles I believe about a year or so old. Got them at a local fish store (sold as freshwater) which I have now converted them into lower end brackish water!

Anyways, my question is about feeding options: I did lots of research on what kind of food they like or prefer but mine started out with blood worms which they LOVE! Then I incorporated frozen shrimp from the seafood market which they would eat till there bellies were like pregnant looking lol. I tried brine shrimp which they at first liked then at this point they just spit them back out like if they don’t like it. They do love there ghost shrimp for sure but that is not going to give them the proper nutrition on a daily plus it will be expensive if I keep only feeding them blood worms and ghost shrimp. They NOW completely ignore the frozen shrimp…;(

They’re both very healthy though. No sunken belly and happy to see me in the morning but why are they acting “picky” with there food.. Any help?

Also they do love their trumped snails occasionally.