Can you post some photos of the hens that are sick, their poop and of your coop/run?
You have 2 that seem sick but how many other birds do you have that are acting well?
What do you feed including treats?
How old are they?
Do they lay eggs?
Re-Check their crops first thing in the morning before they have had anything to eat/drink - the crops should be empty. If they aren't, then let us know what they feel like. Read over the article linked below, this will help you treat crop symptoms if you need to.
I agree if ventilation is poor in their housing, then it should be corrected.
https://www.backyardchickens.com/ar...w-to-know-which-one-youre-dealing-with.73607/