I've never heard of a Guinea pig having "corn" on their feet, but idk. Sure it isn't Bumblefoot?
http://www.guinealynx.info/pododermatitis.html

Bumblefoot can kill a Guinea pig. So I'd get a second opinion.

I have 5 pigs total. 2 girls and 3 boys.
Charlie: Male. White, carmel, and black. 1 year old. Short-hair american.
Lucy: Female. Lemon agouti. 6 months old. 1/2 Short hair American 1/2 Shelti mix.
Wilbur: Male. Golden Agouti. 2 1/2 months. 3/4 American 1/4 Shelti.
Babe: Male. Creme agouti. 2 1/2 months. 3/4 American 1/4 Shelti.
Daisy: Female. White and black. 2 1/2 months. 3/4 American 1/4 Shelti.

All 5 have short hair regardless of the Shelti in them. I think I got all the Agouti varieties correct. There are so many different varieties.

Hi! What cute piggies you have! May I ask what breed they are and how many you have?