What do i do?

My preemie twins have been giving me feeding hell! My boy was throwing up his bottles hours after his feeds, but only ones that were BM mixed with the formula to boost the cal. We got him switched, now my girl is refluxing hours after a feed, she has green watery stool after her feed and had dropped the amount she intakes by an Oz per bottle so... 8Oz a day shes not gaining weight like him (2Oz a day thanks to new formula) and she just seems... More whinny lately. Shes got blisters on her bum from the loose poo, i got so upset last night i threw her can of formula in the trash. Shes suppose to be on Neosure for the cals but i cant keep doing this to her. What do i do now though? She needs extra cals for her weight gain.