Odd Spots & Excessive Gnats

Hey everyone, just about down to the final point of my first grow and running into something that I am not 100% clear on from reading on the forums so I figured I would post 2 pics here (1 of the brown spots and one of the top of the plant right above the brown spot picture for reference).

Overall my setup is fairly simple, and extremely cheap. I will outline it below.

1. Lighting
My lighting consists of 2 dual florescentesent shop lights for a total of 14lumenslumes (not sure if that is the right way to spell it for the light output).
2. My soil is Scott's premium top soil
3. My feed/watering is as such. 4 cups of water 1 to 2 times a week depending on how quickly they dry out. Every 3rd week I water with 4 cups of 1/4 st Miracle Grow

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At this point not looking for any miracle answer but just some general guidance on what this may be as only one of my 2 plans from my original 5 has this, the other 1 is looking fine but is also about 2 weeks behind the plant getting the spots.