Hi Mike,
Thanks for the response. I didn't notice any root issues when I potted it for winter, but too much water is still definitely still a possibility as I have the plant in a seedling mix which stays moist for a very long time.
I was thinking it might be phytophthora as we do have issues with here in Florida and it does resemble the pictures of phytophthora I've seen elsewhere on the net.
Any suggestions for getting rid of it? I definitely don't want it to spread to my other seedlings.