Multivitamins ans minerals for whippets (uk) what do you feed your dog? Different brands sensitive stomachs

Are there any good brands can recommend? Or good but reasonably priced dog food?

I live.modestly, have 2 whippets and live in an area of social deprivation.

We have been feeding butchers puppy food mixed with iams for puppy and older whippet.

I am looking to add multivitamins and minerals or improve food quality. Wondering what others would.advise for a not so rich whippet owner who loves her dogs very much but is on a budget also.