I'd say you have the likely cause identified, wet feet. If there is anything you can do to aid drainage, consider doing that. Otherwise hope for dry weather. If this issue continues think about planting on raised beds next time and get a rootstock that is more tolerant. Lovell and Nemaguard are very sensitive to wet soil. Citation and a few others will take wetter conditions.

Thank you very much, Fruitnut.

Unfortunately, not only I can't do anything to aid the drainage (I planted them on my lawn which is level), I just mulched the darn things this past weekend.

I'll remove the mulch tomorrow and start praying.

Thank you for your advice on rootstocks. I have not paid much attention to them before. I will do now.

I just plan to plant a new peach tree (TangOs) on a mound next year following Olpea's system. It looks like I may need to plant a few more new peach trees if it does not stop raining anytime soon.