Hen with purple comb breathing heavily with an open mouth when she sits down

[OwO]

She is a light sussex around 5 years old and for a few years now she's had a problem with her breathing. When she sits down she has to breath with an open mouth and her comb and wattles turn purple within a minute, then when she stands back up she seems dizzy for a second but then it turns red again just as fast. I was thinking canker or something but I can't really see anything inside her mouth.

 

[nate1the1great1]

Is she acting lethargic? Is she avoiding the rest of the flock and lying in a dark corner by herself. Is she not wanting to eat, but is extremely thirsty?

 

[OwO]

nah she still acts normally for the most part, but some of the time she will just sit on her own in the shade. She still eats a lot and drinks like a normal amount I guess. She's still able to run down the garden with the others when I let them out, albeit a bit slower and more clumsily. She's not laying eggs anymore though and hasn't done for at least a year.

edit: she also sneezes quite a lot

 

[OwO]

anyone have any ideas?