since this recently happened to one of my birds, be aware that when their immune systems are compromised, they are prone to secondary infections, such as fungal respiratory infections (which my poor bird got) and digestive infections like coccidiosis. If they develop addition symptoms, you may be dealing with a combo and may need to treat both.
Your hens face seems swollen, which may also point to mycoplasma. I'd recommend antibiotics (we did vet prescribed as our sick ones were babies, but I've read Tylen 50 injections seems to be the best over the counter) to cover a range of respiratory infections. Also look into environmental concerns, conditions where fungal spores may flourish.
I'm reciting all this as our avian vet told us when we took our birds in. Keep in mind that your bird may be carriers for life, even when not symptomatic, and you may go through this again every time they are stressed or with any new birds you add to the flock.