Get some mites for the gnats. You're gonna reuse the soil anyhow. Living soil WILL have bugs. A few gnats here and there is fairly normal, even in older soils. Other insects like spiders, rolly pollies, centepedes.....will eventually make their way in. At least in my experience. Soil is about 6 years old or so. Any way, the mites will control the gnats. Neem should only be used about once a week for an IPM. You can burn your plants with it. I think it actually clogs the stomata, or has a reaction from the lights. Any way, make sure you shake it very well, and run it under some warm water to mix it. Otherwise it gets concentrated at the bottom. Plants look good. Id also recomemd some worms, red wigglers, and something to use as mulch, or some cover crop. I defoliate alot, so my leaves just get dropped in the soil. Ive used timothy hay, alfalfa hay is a good one.....you can even use some brown cardboard. Anything to keep the top of the soil moist. Not crucial, but will really get the soil biology going.