Any ideas what. the cause mite be…
Your picture didn’t post, does it look anything like this?
Edit: it didn’t link right …search powdery mildew above -good luck
Looks like powdery mildew
I read that milk and h2o 9part1 will do the trick to remove it will give it a go
I read several recipes, I thought the milk recipe said 40% milk/60% water …spray every 10 days?
What cause mold is Realitive Humity - also do you have air circulation - fan/s ? air needs to be replaced every 30 seconds or so
Your grow room is to moist and not enough fresh air moving in and out of the grow room , you need some moisture in veg but you have to keep the air moving , if the air don’t go in and out it will become stale and cause mildew .