Advise please.Something is seriously wrong, my baby is sick big time

.The leaves are turning a slight yellow brown.The tips started a few days ago, i thought it may have been down to too much light as Ive been having problems with my light timer, i cant guarantee that she has been having 18 hours light only.I will know this at 12PM today as I'm off work and will be around to see if the lights turn off.The other thing Ive done recently(last night) i gave a little Bio-Grow(8.0-2.0-6.0) 1ml per 1liter to help her along.The amount given is some small surly this hasn't caused this.Please help guys really need help on this one.Bellow in the first photo is when the leaf tip just started to change color(2 days ago).The rest are from today.
This is a bad pic SORRY
SV300030.JPG SV300033.JPG SV300037.JPG SV300038.JPG