Over the course of the last month I have started two flats and a few pots of Coleus plants as I prep for Spring. Random sprouts have wicked off near the soil level. The first flat of coleus I used a 'home brew' mix of 2 parts course sand to 1 part mushroom compost sprinkled with azomite powder. When these started to wick, I thought it was the mix, so my second flat was done with a store bought mix. But random sprouts in this flat started to wick as well. The wicking isn't from lack of light. I have a good set-up and move them outside in my lanai to get actual sun when weather permits. So I am assuming there is some sort of fungus that is attacking them.

While the sprouts are now starting to go change from green to their other colors, they have not yet formed their first true leaves, so I am hesitant about spraying them. Is there anything that can be done to halt the spread of the fungus? And is there anything that can be done in the future to help prevent the fungus from showing up in the first place?

Oh, and both flats were new and clean, so the fungus did not come from prior plantings. And interestingly enough, the ones started in 4" pots have been fine.