Acid Burn? Yellowing towards center?

Ok, plants are looking excellent minus the fact that one of them has small markings that look like burns on its 3rd set of leaves. Also, the yellowish/green has become increasingly more visible on the leaves and towards the stem? Why is this? More importantly I care about the coloring, because I'm pretty sure I've already lost the one with burns on it, which I think may be due to me putting in the nutes too early. I want to make sure the one without the burns will turn out perfect though... if you must have pics to understand, let me know and I'll work on it. Any advice is helpful, thanks all!

pics please... a nut burn will start on the tip of the leave.. not the middle.. ?
hmmmm ???


picture would be nice : )

Here, maybe this'll help... on the left plant, maybe you have to click it to get a bigger pic... the left plant, on the leaves with a 5 set, the center main leaves are shriveled, discolored, and have that burn look to it. The plant on the right is doing fine from what it looks like... what do you think?

what's your ph? I am guessing it is either to low or,,,

you have a K, MG deficiency,, or both?

It's really high... between 7-8... but i'm nervous to put any acid in it... what do u think?