For each achievement, do all those foods have to be fed to the same pet or can they be fed to different pets? :)

I'm pretty sure for the ones that say like "Feed the following _____ to one of your pets" then yeah, it has to be the same pet.

That makes sense, haha. :)

The black candy bars and oofa fruit can be fed to any of your pets, but I think those are the only exceptions! c:

and the pumpkins for the 'cheater cheater pumpkin eater' achievements. (took me way too long to figure it out, it was taking forever thinking i had to feed all 500 to one pet!)

Ahaha, oh yeah. I forgot to check the seasonal tabs!