1y old polish flock not laying

[ChickenMa18]

I have a flock of polish (1 roo, 4 hens) that are right at a year old. We hatched them last spring and they started laying in the fall. My husband decided they needed a heat lamp so heat lamp it was. *no criticizing please, we know the dangers of using one* about 2 months ago we had one of them go broody and we also gained 2 new hens around the same age from a neighbor after they were being picked on by her other chickens. We quarantined the new ones and the broody one stopped being broody with about a week to go before hatch date. We merged them together everything was fine and dandy right up until they stopped laying eggs.
All of them.
All at once.
I have one that was looking rough (missing feathers) so we separated her and have treated for lice. None of the others seem to have any issues and no lice were found while inspecting. We have since moved their coop and run, cleaned the coop out and treated the coop/chickens a few times. The one missing feathers is still missing feathers. We still aren't getting any eggs.
It does seem as though they might be going through a molt but I thought that only happened in the fall?

Any insight on what is going on would be SUPER appreciated!
Thank you!!!!

 

[MLG1900]

Well, i am not an expert here. But if you think they are starting to molt again, that would be good enough reason for them to all stop laying. I wonder if having the heat lamp in the coop had anything to do with messing up their normal molting cycle. Most times when I am missing eggs, it is because I have alot of snakes getting in. Last year I caught 6 snakes!

 

[ChickenMa18]

I figured molting was good enough of an answer but always like to check that I'm not missing anything. We have never done heat lamps with adult chickens before so hadn't a clue it could mess with their schedule, other than them laying. I figured if it was lice the others in that flock would be showing symptoms?

I am pretty certain it's not snakes, I have two dogs that hang around the chicken pens and are pretty good at sniffing out snakes and letting me know about them. And we check randomly throughout the day...

 

[aart]

Did the one you treated for lice actually have them?
If they are molting, you will see new pin feathers emerging.
Lots of changes, they don't like that, and it can definitely affect laying.
How exactly did you quarantine and integrate the new birds?

How big is the coop and run, in feet by feet?
Dimensions and pics would help immensely here.

Do you free range at all?