Keep the fattest one, cut the others close around short. It will grow like crazy then normally. I don't know if it's grafted, here in Europe they usually aren't. So then you'll have peaches maybe next year.
You can also saw or cut some promising upshoots loose. I'd start at the outside where the roots are a bit thinner. A wrist thick
root, i don't know if it will be so handy to replant. I like to keep them in pots on the north side of the house. They need to develop smaller roots during a season. If they colonized the big ish pot of 5 liter if you know what a liter is, they'll be ready to replant in autumn.
But yeah, they might not be valid, i don't know the fungus... But if it wants to live, i'd give a few a chance.
I've got maybe fifty peach
trees grown from seed. I love them. They need no watering.