Weird Leaf Color

Hello fellow grower, judging by the pictures and the leaves on your plant You're either running into a deficiency or your plants are getting locked out from nutrients due incorrect pH range in your soil. Nats are very common in horticulture and don't cause major issues unless the numbers get out of control. When I start seeing gnats I use yellow sticky pads in each of my pots to reduce the population of gnats. If the population still climbs and gets out of control you can look into beneficial nematodes for your grow. Myself and others have had very good success using beneficial nematodes to control gnats. But to me this issue like I said looks more like a deficiency or pH issue. To make sure it's not the pH issue either use a pH soil meter to check the soil or simply water with a pH of 6.5 and measure the pH of the runoff ( water that comes out of the pot ). If it's out of the range of 5.8 to 7.0 then that will be your issue. If the runoff of your pH is within range then you may want to look in to feeding your plants with some high quality nutrients. Hope this helps! 👍