Yikes!
The other two both have small white fibrous looking hairs around the stem; I wasn't sure if I should chalk it up to more mold or if this was somehow a part of the young stem. If the other two plants begin to show similar symptoms I may need to scrap this spare potting soil and the cups and wait till I get quality soil to germinate some of my new seeds into a better pot.
Something I was thinking about as I read your post is the bag of soil I had "sitting around" was in my cellar, unsealed and I am sure if microbes/small bugs wanted to make their home there they could have.
It may also be a good opportunity to clean the inside of the box with diluted simple green and then once the ac/dc adapter arrives actually finish the box construction so I am not doing this sub-par.
The bad news about this is I think I only have two remaining "bag seeds" that have been slow to germinate or have not germinated at all and if I am still making adjustments I don't want to germinate my quality beans that I spent hella $$$ on.
I do have the small bag of Mykos as well but I was planning on saving it for my quality soil. Would something like this help protect the seedlings from malicious bacterium and possibly small bugs too?
Definitely the soil man. It probably even has an expiry date, they put mycorizal in lits of Potting soils, and there's a good chance it was infested with micro bugs that feasted on your seed. Get yourself a fresh bag and you'll do fine for those last 2 seeds. For now you can try and treat your seedlings with a mild food grade pesticide. Hope you keep trying and trying until you can confidently grow some premium seeds. I did the same thing, as many of the folks here also did. No worries mun
KiG cheers
Ps.. Edit: the hairs on the stems are totally natural though.