Mold when starting seeds?

[Ruby]

I started some seeds (Craig's method) and after about 4 days I have some greenish mold growing on top of the mix (just a tiny bit in one cell). It's not dark green, but sort of greyish green with a little bit of white fluffy looking stuff (again, not that much but in more than one cell).

This happened a couple weeks ago in a deeper flat of seed and I watered with a diluted hydrogen peroxide mixture to make myself feel better, but I wanted to find out maybe what I should actually be doing in this case.

I don't know if it's just something in the air (yesterday and today have been cold and rainy). I'm pretty sure it's some combination of air temperature/moisture and possibly contaminated seed.

Anyhow, I'm not too concerned, but I'd like to know the best way to treat this at the point I'm at now without throwing out the tray. I've taken off the plastic wrap (it was loose, for air circulation) because some seedlings are popping up. Seaweed extract? Hydrogen peroxide? Baking soda? Cinnamon?

I thought it was a fluke the first time it happened, but it happened again so I thought I'd ask. Perhaps others have had the same issue.