Emma Miriam
Chirping
A 6x8 coop should really only hold 12 hens, 15 at most...so perhaps you could do a little coop addition. 8x8 would be the absolute minimum I'd go with for that many hens...and if you're adding, you might as well go bigger! 8x10 would be a good size.
Your coop looks nice, though. Ideally you should have 1 foot of roost space per chicken: in cold weather they'll huddle, but they like to spread out in warm weather. If you don't have super hot weather where you live, 8" per bird is fine. And yes, 1 foot from the wall is typically fine
Also, make sure your roosts are 2 feet below your upper ventilation: you don't want breezes blowing on roosting chickens. So I wouldn't have your roosts any higher than 4 feet off the floor. How high are they currently?
You said you have two 4x8 yards for the chickens to roam all the time. Are they predator-proof? Do you close the door to the coop every night? Could you describe that setup a bit more? Also, do you ever let the chickens roam freely around the entire yard, or are they always in the coop/run?
Your coop looks nice, though. Ideally you should have 1 foot of roost space per chicken: in cold weather they'll huddle, but they like to spread out in warm weather. If you don't have super hot weather where you live, 8" per bird is fine. And yes, 1 foot from the wall is typically fine

You said you have two 4x8 yards for the chickens to roam all the time. Are they predator-proof? Do you close the door to the coop every night? Could you describe that setup a bit more? Also, do you ever let the chickens roam freely around the entire yard, or are they always in the coop/run?