Flock Twitching Their Heads

I've been pouring over these forums for what might be the cause of this but my Urban Flock of 5 hens has been twitching their heads this summer since moving out into their coop. They're 19 weeks old and have been in their coop for a little over 2 months. During this time they developed this little habit of twitching their heads frequently. After digging around I came to the conclusion that it might be Gapeworm but looking at all the other symptoms that people mention for Gapeworm and all the other things I've found online they just don't match up to my flock.

Symptoms:
Twitching heads although not violently.
Neck stretching and open mouth yawning although not very often. (I've always considered this crop adjustment or just yawning really.)

Symptoms they DON'T have:
No raspy breathing.
No lethargic behavior.
No runny eyes.
No sneezing.
No weight loss.
No strange foamy poo.
No signs of mites, lice, or other parasites and no issues with my dog who is out in the yard daily as well in this regard.

Climate:
I live in Northern Michigan and it has been a hot and humid summer but we're maintaining mid-80's right now with a decent amount of humidity this summer.

They look and appear to be perfectly normal 19 week old hens. In fact one laid her 1st egg today and another appears to be close behind.
Check out this video. This is not my chicken but happens to be exactly what they're doing.


So before I go down a de-worming route on 19 week old hens can anyone chime in with what might be going on here. Thank you all on your comments and suggestions for my little girls.

 

Thanks for the replies. I thought my flock was listed in my signature line but let me re-post just in case.
1 - Easter Egger / 2 - Australorps / 2 - SL Wyandottes

The video link I posted is not my own chicken. It just happens to be a chicken doing the exact same behavior that my urban flock of 5 are doing. They are in permanent confinement with twice the amount of square footage suggested per hen out in the run and 1 1/2 times the suggested square footage in the coop house.

I will take your suggestions and do a search on ear mites and "attempt" to check for gapeworm using the q-tip however this can be a very difficult and stressful task that I'm not looking too forward too. I just want to rule out a few things before treating for worms using a broad spectrum dewormer. 2 of my girls just started laying their first eggs today also so I don't want to also add stress to them by the worming treatment right now.

I am happy to think it isn't gapeworm because it appears to be something that comes on hard and fast with many symptoms and will cause mortality if not treated. My girls have been acting like this for a couple of months now so that's a plus "against" gapeworm. Thank you for your suggestions. Please contribute if you have some of your own suggestions or stories to share.