Picky Hermit Crabs? Seem happy and healthy, but wont eat!?

I got two hermit crabs about a month ago (Michael Jackson and Cee Lo Green...my four year old named them!) just a few days after getting them they went under to molt, which took like 3 weeks. They have come back up from their grave and are now happy and social and active. But they will not EAT! They ate a shrimp tail once, but not the next time I gave it to them. I have tried carrots, strawberries, crackers, pirate booty, freeze dried blood worms, cheese (before I knew it was bad), lettuce, apple, grape, sunflower seed(desperate), dried cat food.... I don't want to do store bought food because I know it has bad preservatives in it... but I want to try it out of desperation. Is it normal not to eat for periods of time? OR they don't like anything I've offered?