whats this?

Just curious if anyone knows what this faint discoloration means??

that looks like powdery mildew to me from the pics. if so you need to lower the humidity and look into using some baking soda water mixture to try to get rid of it. if you have some good tops that have no mildew on them take some clones and seperate them from the plants and once they root and you trans plant cut any mildew away from them and keep the rh down. good luck thats a tuff one to get rid of.

it doesnt seem like any kind of mold or mildew. It more looks like a discoloration in the leaves. and its only on this one plant. All the otehrs seem to be normal. And speaking of colors, is it normal for one plants foliage to be different color from another plants if they are the same strain???

the first closer up pics looked like it was on top of the leaf the new pics look like in the leaf. usually the darker one means that it is getting more nutes and the lighter one's a little less. if you only have one that is darker than the rest try flushing it for a couple days with straight ph'd water . the lighter green one looks to me like it needs more nutes or the ph adjusted and the lower leaves need to be up out of the dirt or you will have problems there later to. is it possible that one it getting more light than the other? more nutes or the bottom of the watering jug where it is more concentrated?

Its a slight def. Nothing to worry about there.