Nitrogen deficiency?

This is a Jack Herer being grown 12/12 from seed in some potting soil + perlite (not miracle grow) and in an 8 inch container. Its about a month old now. About a week ago I noticed the bottom leaves turning slightly yellow and fed the plant for the first time, 1/4 strength AN Jungle Juice Micro, Bloom, and Grow. I waited about 2-3 days until it needed water again and fed it the same strength, and that was about three days ago. Growth has pretty much stopped/really slowed down. I don't think I should have fed twice in such a short period, bu anyways... Here is the plant now. The leaves are still yellowing a bit higher up and there is (I think) some small nutrient burn on some of the leaves. Can anyone confirm, and help me get my plant growing again?

Imgur album- http://imgur.com/a/ZKh0W

Also though I might note, I have had some fungus gnats. Not a huge amount of them, and I've been taking care of them and such, but is there any way they might have something to do with this? They really seem to like this plant, so that's why I ask.

Bump for visibility...