Those look like leathers, they shed and thats normal. It is how they clean themselves and it is also a protection, they look stressed. Did you just add them?
Kents microvert will work great to feed them. Any coral food for filter feeders will do.
there isnt a need to feed ur soft coral, but feeding it wouldnt hurt. one way to feed softies is by under skimming. leathers like organic matters in the water.
I agree they need time to adjust to the environment you just recently introduced them to. As long as they have moderate to high lighting, good Calcium and Alkalinity levels they typically do very well. They can obtain nutrients like Phosphate and Nitrate directly from the water column so feeding them directly is usually redundant.