you've got 1 of several possible things happening.
No it's not molting if they are completely bald, they will molt in a manner where they stay at least covered with feathers.
here's some of your possible problems
with feathering, bald and red usually means mites or lice. Lightly dust them with Sevin Dust (for those who will say it, yes it's a poison but it's harmless, used it for over 35 years here)
heavy breeding can do it too, but on the back of the hens, the roos should have no problem.
Feather picking due to being over crowded or being feed a poor diet low in protein would be my second guess. Be sure they are getting a good level protein feed, corn and scratch feed aint it and is a very poor primary diet. A Maintenance or layer ration should be fed to all birds. Some times if feather picking has been going on for a long time, the birds will develop a taste for it and will continue even after the feed has been corrected. At this point you will have no other choice but to either put blinders on them, or cut the top part of the beak back so that they cant grab feather very well, works great, grows back and usually will stop them. Just cut it back to the "quick" basically the fleshy part, you usually can see the area, it will be darker, usually just the tip is somewhat clearish, that's what you want to snip off.
Now for the poop. Yes worm them, there are many products out there, Safeguard and Ivermectin are some of the best, doses will vary, but neither of those are water soluble, so give them a direct oral dose. Some will tell you they can be put in the water, but they will not get a good dose that way. Safeguard fall out of solution in a matter on minute and will settle at the bottom of the bowl, Ivermectin will just fall straight to the bottom. Usually 1/4- 1/2 cc per bird works great depending on age and size, bantam 1/4 large fowl 1/2
The diarrhea can be from one of a million things, yellowish foamy runs are usually signs of intestinal parasites, but yes antibiotics should be given too seeing how these are new birds and you arent sure what they have been exposed too. You have done great by quarantining them. Keep that up til they are all healthy and fine looking for at least 30 days.
Hope that helped a bit