Let's hope it's not those little bastards bro! Check your sticky traps real good for tail pipes on their hineys, the flyers look very similar to adult gnats ....the crawlers if in the soil can be different sizes and colors like ....clear, white, reddish brown, green, or black.
Most of the time peeps have RA they have gnats also! One sure fire way to tell if you have RA flyers in there is to watch the space between your lamp and your canopy ....are there flyers shooting up & down? If so those are RA
All my plants would look good till week 4 then they would start going downhill from there!