Help! Bantam has a sore mouth

Cora, my 5 year old Bantam Mille Fleur Hen, has developed as swelling on both sides of her lower beak. Two weeks later, she developed swelling above her upper beak at the base of her comb. The swelling has been gradually getting larger.

I have tried treating the swollen areas with peroxide and polysporin (antibiotic cream), however the distress and pain that it caused the hen prevented me from trying anything else.

She is eating well and is active and will allow me to examine her mouth, but is still in pain.

I have raised chickens for 30 years and never seen this before. I need ideas about how I might treat it, or even an idea what could be wrong so that I can research it. She is otherwise lively and laying well.

The average lifespan of this line of Mille Fleurs is 8 to 10 years.

I would appreciate any help I can get.