but! As someone who is trying to buy and feed a lot of items to one pet, it's very, very time consuming to search up the items in their nourishment, see if it's been eaten, and if it hasn't try to buy the item from the shop before someone else does.

It would be cool if it showed in shops if active pet has interacted with the item already. Or even in the inventory! maybe clicking on the item in your inv will show "(pet) hasn't eaten/played with/read this yet)