leopard geckos question please help

ok well ive looked around and apparently i got screwed getting my leopard geckos on craigslist and i have 4 seriously skinny geckos ive removed them from the sand and started giving them mineral oil incase of impaction. they have dusted crickets and extra calcium in there cage to lick. what else can i do for them to fatten them up and get them back in health any help is appricated greatly! thank you in advance ps been watching after feeding and havent seen 2 of them eat. have tried diffrent size crickets

I've always offered waxworms to skinny geckos. They're like the fatty Big Mac of feeder insects.

THANKS

dont feed them to much wax worms too many can kill them