I don't want to read 3 pages of whatever, so here goes;
It just looks like light burn.
I'm guessing you had the light about 1"-2" away.
Just back it off like 1/8"-1/4"
If your soil has "Dolomite Lime" mixed in with it, then don't worry about pH.
Dolomite Lime naturally neutralizes pH to 7.0.(Neutral)
Oh and when your plants get bigger, you'll see spots like that all over the place.
It won't matter unless it gets worse.
I know nothing about kits,
just get an organic combo of
Vegetative/Growth/Leaf fertilizer. These usually have a really good balance of N-P-K with a higher Nitrogen level.
Flowering/Bloom/Flower&Root fertilizer. These are usually more unbalanced and have a lower Nitrogen and higher Phosphorus(P) / Potassium(K) levels.