Some days just aren't pretty.

Violet developed a rash about three weeks ago shortly after eating a jar of sweet potatoes. So naturally we stopped feeding her sweet potatoes. Since then the rash has come and gone almost daily. Usually you can't see it but about once a day we notice it flares up like this for about an hour then goes away again. I am at a loss for what causes this. She gets it on days she gets jar food and days she does not. Days she gets a bath along with the days she does not. From the laundry with her detergent and from laundry with no detergent. I just don't get it. So here is a picture. Please. Any ideas? It looks like this for about an hour then just disappears until the next flare up.