Hey guys so plant's are doing pretty well but...

It looks like you have a ventilation problem or humidity

If you think its mold or some kind of organic life, the easy way to check is water a bit less often for a while, if you normally water every 3-4 days switch to 4-6 if possible, and allow the soil to dry out more before watering again. This will do two things. 1. roots grow bigger quite a bit faster. and 2. If you have unwanted microbes, they tend to die off from lack of constant moisture. If it dies off then it was alive. If it doesnt then its salt or mineral build up. Unless it starts spreading id not worry yet. like I said Ive seen similar before, as well as even getting a fuzzy layer of fungus for a week when I added milk to my compost to boost the minerals and nitrogen in it. Once the soil dried out a bit the fungus dies right off. the white stuff on the old soils and composts tends to be on the drier parts of the mix. Like the larger bark chips.

Stop playing, when you see this powdery substance, take it out of the pot as fast as possible. Keep it clean.

Dont worry about it. Any older soil or compost or manure left in a bag for a while half open ends up looking like this too. I have a near empty bag of mushroom compost that looks like this as well and its been half open for months. Never had issues using it before either. Just put some of it in my current Auto grow soil, Im not sure if its salt or mineral build up or dried fungus/mold, but whatever it is,, its so common and harmless id not worry. Always seems to be store bought bagged soil that does it thou.

@Chuky324 should I worry?

Hello. I think it's mineral salt build up. The living soil fungus is whiter. Chuck.