Fortunately this is not a problem we faced, but I would just experiment. You can also check for key ingredients on the side of the product. Also note that the ingredients list can differ wildly between same brand formula across different countries. In my opinion stay away from anything that is made in the USA.
You can change to brand like Nan Optipro, Enfamil, S26, Dulac, Lactogen. If baby keeps having diarrhoea then perhaps she/he might be lactose intolerant hence you need to change to soy milk/goat milk or lactose free formula.
Baby could possibly be lactose intolerant. If similac HA TC still causes diarrhoea , can try goats milk which has lower levels of lactose otherwise Isomil (:
My baby also had diarrhoea after taking kendamil, switch to Bellamy and she is fine. I think need to try out to know how baby reacts .
Goats milk or if not soy milk
Try Enfamil, S26,