I'd treat them for mites and lice, and also deworm them. I'm sure that in such terrible conditions they have picked up some internal parasites. Valbazen and Safeguard are two good dewormers to use, and should kill most/all worms.
Definitely quarantine them for two weeks or so. They might have a contagious disease. Watch for signs of sickness like lethargy, discharge, sneezing, coughing, strange droppings, lack of appetite, and any problems egg laying (if they are laying). Watch your other birds carefully too, to make sure that they aren't gettting sick.
Check them over for any signs of disease now. Feel their crops: are they squishy or hard? If squishy, they might have sour crop, if hard, they could have an impacted crop. These ailments should resolve themselves with good care and treatment, if neccasary. Also feel their abdomens, to make sure that they aren't egg bound.
Give them some probiotics and electrolytes to help them get over the stress. They might also enjoy foods like yogurt, applesauce, moistened chicken feed, and scrambled eggs. Give them free access to feed and water.