Mouth Sores?!?

In this shot, you can see one by her nose.

A few days ago I noticed a little sore on Morrissey's lip. Today there were more. I have no idea what this could be. Does anyone have any ideas? It is on both sides of her mouth. They don't seem to be bothering her. Nothing in her diet has changed recently. The weather has gotten much colder, but I don't see how it could be related.

Today we worked on moving away from pressure and general ground manners. She was amazing! I've been meaning to work on how mouthy she is, but it is hard to tell her no. She constantly wants my hands in or near her mouth, but she never bites. She reminds me of a goat. She tried to bite the button off my jacket. When I told her no she let it go. Who knows what she is getting into in her pasture that is causing the sores. I've looked at all the plants in her pasture. They look the pretty normal... dead, but normal. Maybe it is something in her round bale? I'll have to check it out.