This happened with my skittles,
I thought he wasn't drinking, and people on AA said check the poop, if it's runny he is hydrated, if dry then not, skittles poop was dry, so what I did was I introduced the water bowl to him. I grabbed it and offered the bowl near his neck, nd I would splash it a bit, and then would sort of push it to him ( as a way of saying go on have some!) also talk to him and make noises like "Oooooo, Yumm Yumm!" and he might dip his beak and have a look, if not, put it back in the origan spot, after that, skittles came and drank, and no more dry poop
As for food, i was also giving skittles millet, and so he took no interest in his actual food, so i took skittles out of the cage and repeated the water thing, and maybe pick bits of fruit/ vegetables from it and feed them to him in your hand, and that's how skittles started eating. Now he wakes me up every morning, and wont stop screaming until he gets his breakfast!
Good Luck!