Good input fellas. A few answers now...
I do have a few Fungus Gnats, but not heaps. I keep an eye on them with yellow sticky cards and periodically use some of that GNatural. I don't think there is enough gnats to be an issue. I did overwater earlier, but gnats have faded as the soil dried out.
Someone mentioned White Flies, I've never found a bug in my tent that wasn't a Fungus Gnat or an occasional ant or spider. No flying bugs except the gnats. The "white stuff" I think might just be reflections off the foliar spray droplets.
Someone also mentioned VPD and measuring the temperature from the leaf surface vs the tent air. Admittedly, I'm just using the air temp and I do know that the leaf surface is a more accurate method. However, even if the leaves are a couple degrees cooler than the air, the VPD is still in a comfortable zone. I've got my new AC Infinity fans, humidifier, and controller running and my tent has never been more stable. I reckon temp/RH/VPD are probably not the issue here.
I'm most suspicious of either a N-toxicity or K-deficiency. Maybe one of these nutrient issues could have been caused by the earlier overwatering? If I've got too much nitrogen, and this seems a good possibility, I think plain watering is my only real option. Just watering and waiting for the plants to use the nitrogen up. Unless there is something organic I can add to tie-up some nitrogen?
I can get my hands on a soil test kit that does NPK+pH. Might give us an answer or at least rule out some possibilities...