I spoke to Doug on the phone today and, just for the benefit of anyone else who might be having a similar problem, I'd like to recap the symptoms that Guadalupe is experiencing and the treatment that we discussed as an option.
Guadalupe has a crusty, dry, swollen skin condition on her face. There is no exudate from her eye or nose, there is no sneezing or coughing. Her eye has been swelling shut but this is due to the swelling and crusting on her face, not discharge from her eye. This has persisted for two weeks and none of his other chickens have shown symptoms. Guadalupe is now beginning to shake her head. I told doug that it looks and sounds like a fungal or parasite issue of the skin. The ideal scenario would be for him to have a skin scraping looked at under the microscope to check for mites, yeast or fungus. In the absence of that option, Doug has given her some ivermectin and is going to apply it topically also for five days. If that doesn't work, we're going to discuss furthur options. He has been applying triple antibiotic ointment which has kept the skin pliable and not let it get overly crusty but it hasn't improved the condition. If the ivermectin does not work and there is no change after five days, I may suggest a miconazole ointment.
If anyone has any further thoughts or suggestions, I believe that they would be appreciated.
Just an update, Doug took Lupe to the vet and the vet came up with sinusitis and put lupe on Tylan. In my opinion, Tylan is a little too weak for a sinus issue. I have had more success with erythromycin and nebulizing with gentimicin.
Oh, here's another thing that an avian vet I used to work for told me to do for sinus issues. Vitamin A: I make up a mush of vanilla wafers (because chickens love them), Kale, broccoli greens (the leaves on the broccoli, not broccolini or rapini), garlic and olive oil (because they have antibacterial properties that bacteria can't build up a resistance to). Then I sometimes add some chilli powder because it also has curative properties and birds love it.
I give this along with the antibiotics and some probiotics, but not yogurt because yogurt stimulates the production of mucous and when we're talking about a sinus infection, mucous is the enemy.