If they are molting then they will stop laying, but you should be able to tell by their feathers. It seems more likely that they are just stressed.
The first thing I'd do is make sure their is no mold in their food, or algae in their water. Clean both containers out with some bleach to disinfect. Clean the coop out, perhaps disinfect it as well. When the coop is clean, sans bedding and straw in the nesting boxes, I spray Permethrin (basically flea and tick spray) all over the wood surfaces to kill parasites and ward off flies. I would do all this not because there may be some viral infection, just to give them the most healthy environment. Also make sure they have adequate ventilation in the coop, and consider propping windows open wider for the summer.
As stated, check for mites. Additionally I would examine fresh poop for worms or diarrhea/blood. If you suspect coccidiosis or worms then post in the medical section for more specific help. As I understand it, any stress can affect egg laying, and it can also make them more susceptible to parasite infestations or other illness.
