One of the girls had surgery for sour crop she has lost some weight & her sisters keep her from eating & drinking. She’s been home about 2 weeks & was gone for 3. What can I give her to help her put on weight?
If the other chickens are keeping her from eating and drinking, then start by separating her. A cage or crate inside the chicken pen might be good--so she can eat and drink in peace, but not feel lonely.
It sounds like she doesn't need special food, she just needs to be able to eat in peace.
If it took her several weeks to lose the weight, it might take her some time to gain it back--but you want her to regain muscle, not just fat, so do not try to rush her too fast.
Best food options:
--her usual food
Water and grit available at all times.
Sometimes a hen will eat a bit more if you get some food wet with water.
If she is laying eggs, or is old enough to do so, then it's a good idea to give her a dish of oyster shell too, so she can get whatever amount of calcium is right for her.