OOOOH!!!! My guess is the the Tubster is, in fact, a BOY!!! I could be wrong - but in the picture it looks like there are small pinkish 'pimple' under his arm? If there are, these are called post auxiliary subdermal glands - and only the males have them :) I'ts possible they could be different ages, and that could have something to do with the size differences, too?
You should feed them once daily, mine seem to prefer getting fed in the evening (which would be their feeding time in nature) and reward me with a ton of activity when I feed them at the start of their most active time of day. The 'rule' seems to be that once the frogs hit maturity (usually at around 9 months of age) to decrease feedings to every other or every third day . . . that said. . . I still usually feed mine once daily, cuz' I like to see them eat! But I've been trying to cut back to every other day lately. I'd really hate to over-feed them and cause any issues :)