I'm growing three white widow plants in 20 gallon planters with miracle grow soil under a 1000W HPS bulb. They're about three-four weeks along.
Unfortunately the soil was contaminated with gnats. I've done my best to exterminate them without harming the plants, covering the soil with steel wool, letting the soil dry out and turning the grow fan on higher than I'd like it, but they're still maintaining a small presence, albeit not as pervasive as they were a week or so ago.
So far I haven't given the plants any nutrients. Then two days ago I noticed these yellow spots appearing on the third and fourth sets of true leaves -- on all three plants. -- Any ideas what's causing it and how to remedy it?
Unfortunately the soil was contaminated with gnats. I've done my best to exterminate them without harming the plants, covering the soil with steel wool, letting the soil dry out and turning the grow fan on higher than I'd like it, but they're still maintaining a small presence, albeit not as pervasive as they were a week or so ago.
So far I haven't given the plants any nutrients. Then two days ago I noticed these yellow spots appearing on the third and fourth sets of true leaves -- on all three plants. -- Any ideas what's causing it and how to remedy it?