In the photo, is that the "goo" dripping out of her mouth? Why do the combs, face and beaks of both look shiny/wet?
As suggest by the previous posters, your problem could very well be mold/fungal.
Your girls with goo coming out of her mouth may also have a crop issue.
Sneezing for weeks makes me think dust/ammonia/fungus/mold. You mention eyes watering up around roosting time. You also put a heat lamp in the coop? Are you brooding any chicks in the coop? What is the heat for?
Excess poop can create ammonia which in turn would cause some respiratory symptoms as well as watery eyes. The hay mold/fungus would create the same situation.
@aart
is great a helping with ventilation concerns, you may want to post some photos to see if adding some ventilation may remedy some of your problems.
Check the crop of your girl with the goo coming out of her mouth when she goes to roost - it should be full - check it first thing in the am - it should be empty. If they odor is coming from her crops them she may have a sour crop.
Here is some great info on crop health and treatment options:
https://www.backyardchickens.com/a/impacted-slow-and-sour-crops-prevention-and-treatments
http://www.tillysnest.com/2012/01/crop-issues-html/
http://www.the-chicken-chick.com/2014/06/chicken-anatomy-crop-impacted-crop-sour.html
http://www.the-chicken-chick.com/2012/04/answers-from-chicken-vet-on-impacted.html