Plants look pretty happy to me too. You mentioned possible gnats in the soil. DE or Gnat Nix helps prevent prevent the adults from getting into the soil and laying their eggs. Their larvae eat the roots and can cause leaf and overall health issues. You can use gnatrol and drench the soil per the instructions. My understanding is Gnatrol is basically BTI, same ingredient in mosquito dunks and is safe for use in flower. I'm not an expert, but gnatrol and yellow sticky cards has killed gnats for me successfully (and ATU too). You may want to let them dry a little after the flush you gave them, then drench with the gnatrol per the instructions and hit them every 7-10 days for 2 or 3 applications.