Strange color from leaves. Not nutrient burn. *Pics included!* Please help

So this plant is about 6-7 weeks old and last night I topped it using Uncle Bens topping technique to get 4 colas found in the advanced marijuana growing thread. Its only been 14 hours since I topped the plant and now on the second leafset down I have some strange almost gray residue looking stuff coming from the stem of the leaf. Its not a residue however as I tried to gently wash it off. Any help or information would be greatly appreciated.
The first picture shows the plant, where topped and the discoloration. The second one shows a closer view at the top. The third is a close-up of one of the leafs.

what are your temps ?
what kind of light ?
soil ?
food?
it looks to me like spider mite damage, only it wouldn't have happened so fast . take a very close look at the undersides of the leaves and the top of um and see if you can see lil bugs clawlin around. ? There might even be a tiny bit of web right by where you see that yellowish.
If its not that , they also look kinda heat stressed.? Or maybe even too much food, or a number of things. Dont forget to check out uncle ben's thread about Plant moisture and stress.
Just answer my few questions and sombody here will help!

Meh, need more info like the poster above me said. If I had to guess I would say minor nute burn from the soil. Possibly pH issue.