I was watering my seedlings tonight, and noticed the oddest thing I've ever seen in my years of growing tomatoes. I sowed the seeds pretty shallow, so as the seedlings grow, some of them sort of start to push themselves out of the soil. I was trying to get one plant a little deeper, when I felt the oddest thing. At first, I thought it was just some sort of fertilizer pellet that came in the soil mix, but as I tried to move my finger around it, I discovered the whole root system of this one plant is surrounded in what looks and feels like very firm-set jello, Gummi Bear stiffness level. It surrounds the roots and extends a good bit beyond in all directions, (a little larger than marble sized, but irregular in shape).
Since it was dark and I was pretty grossed out by this time, I didn't really explore it any further tonight. I wanted to come on here and see if anyone has any idea what this might be. Is it some sort of fungus? Pest? For what it's worth, all the seedlings in that pot look very healthy. They are around 3 inches tall. I've had no damping off or other signs of problems, and have yet to lose a seedling this year. The leaves are all healthy and green, and they seem to be growing just fine. A couple of the pots, (not this one), have a little green around the very bottom, but I think I get that every year.

I have them sowed in Dixie cups, with a potting mix. They have been in my kitchen window and have not yet seen the great outdoors. What do I need to do here? Will the plant be okay? Will this spread to my other plants? I had planned on separating some of them out this weekend anyway. I've certainly never seen or heard of anything like it before. Leave it to me to get some strange plant affliction.