founder

Found out today off old owner of my mare that she had founder before what feed can I give to my mini that wont cause this problem and what food to stay away from

Most minis don't need grain at all and do just fine on grass hay.

You'll also want to keep her off lush pasture, since that can cause her to founder again.

If you want to turn her out, either do it in a dry lot or put a grazing muzzle on her and restrict her time out on grass.

Minis are the very definition of easy keepers, and it's extremely easy to founder them because of their size.