Leaves turning yellow!!!!

I'm a newbie and I can not find a straight answer for this .. I am growing Northern lights x Skunk, my plant is about 2 weeks old and the bottom cots and one fan leaf have started turning yellow. I am under 2 4ft flourescent 1 warm and 1 cool 6500k ph is around 5.8 to 6.0 and I haven't been using any nutes and I'm just watering like once every 2 to 4 days. Humidity is at 40% and temp stays at around 75* degrees. And I am in a 4x4 rockwool cube which was soaked prior to seed germination. I have 4 other plants under the same set up which seem to be doing fine but for some reason this plant just started turning on me, which is crazy because it started off my best looking and strongest seedling.. At a stand still PLEASE HELP ME IF IT'S NOT TO LATE,, trying to figure out how to post pics right now , give me a minute

Just taking a guess here... Sounds to me like it may respond or be helped by a small amount of nutrients. When I started out my brain went stupid by thinking "more is better". And for years I wondered why it came out tasting like chemicals. DUH! I was giving it 1/4 teaspoon of Superthrive per gallon! The directions suggest 1 drop per gallon.

I paid too much for premixed nutrients - Way too much! The product is highly used and recommended = The thing is they mix a very low solution of NPK for both veging and flowering.

I've just started not adding NPK solutions EVERY time I water.

I have a friend that has grown for over twenty years and laughs at me spending money on NPK products. He uses water straight from the hose and gives them a can of Dr. Pepper sometimes during flowering. His herb is okay sometimes and sometimes I can't believe how much people pay for his stuff. He and many of his friends take heavy prescriptions and alcohol all day so they just "think" the herb is good. Go figure...

to post pics click go advanced than page down you will see manage attachments from there follow directions

Sounds like they need nutes.. Nitrogen

Going to try add some 1/4 strength nutes and see what happens..... Thanks guys

New pic try out

get your light closer for one thing

Sounds like nitrogen, can't tell without pics, just got over a gnarly n deficiency myself. Just give it nutes at half strength and wait for it to respond...