Fuzzy spots on stems...

[SummerSky]

I just noticed that some of my tomato seedlings have what looks like fuzzy spots on their stems and even on the underside of some leaves. The spots scrap off easily and show what looks like healthy tissue to me. They are only showing up on some of my Polish Linguisa and Opalka seedlings. I have about twenty other varieties that look normal. I haven't grown these two varieties before.

They are almost a month old, and I just planted them up with an organic potting soil (Green Envy brand) a few days ago. They are inside under lights (the weather is not working with me). The other night, my husband turned the fan on and didn't realize it was blasting right on my seedlings, so they got knocked around for a few hours but they seemed to recover just fine.

Can anyone tell me what's going on? I've started tomatoes from seed only a couple times, but I don't remember any looking like this...

This is the first time I've tried attaching pictures to here, so I'm hoping they show up...

The first picture is of a Grandma Mary's Paste that has a normal stem. Same age, same potting soil, same pot up date, same flat. The other two are of two different Polish Linguias seedlings.