AsNoriuanswered grow question 3mo ago Think its thrips,  despite you calling them gnats. Gnats fly, thrips  hide underneath  of leaf, could be huge problem. 
When i met them first time, i noticed  at start of flower. Ladybugs and few natural  predators  sorted issue, but my harvest was 20-30% lower than i would expect.
Sort it asap, have sticky  traps all around grow area as prevention.
Good luck !!!