Does anyone know what kind of deficiency this is ?

I've noticed weird brown streaks on some leaves, does anyone know why it is doing this?
http://i.imgur.com/2uHYF.jpg

The plant looks fine overall, but note the brown dots on the leaf at the bottom there
http://i.imgur.com/DivkM.jpg

Another spot where the marks are appearing, this time a different pattern
http://i.imgur.com/qW53p.jpg

Also does anyone think the plant is a little short for 12 weeks (20inches I would say)? I just put her in flowering last week. I've been feeding her fairly lightly, and watering her between every feeding (so nute-feed-nute-feed,etc) something I used not to do

spider mites bro you better fix it quick

If you are using synthetic nutes I would only feed once a week. You also need to flush them with good clean water.

what size pot is it in

Look like mag def. Spidermite are usually at the top of the plant and I dont think its mites neways. Ill grab a pic of mag def to show......View attachment 1989022

found this for you just in case I'm right... Magnesium [Mg] deficiency is pretty common since marijuana uses lots of it and many fertilizers don't have enough of it. Magnesium [Mg] deficiency is easily fixed with ¼ teaspoon per gallon | 3.5 liters of Epsom salts [first powdered and dissolved in some hot water] or foliar feed at ½ teaspoon per 0.25 gallon | 0.8 liter. When mixing up soil, use 2 teaspoons dolomite lime per gallon | 3.5 liter of soil for Magnesium [Mg]. Magnesium [Mg] can get locked-up by too much Calcium [Ca], Cl or ammonium nitrogen. Don't overdo Magnesium [Mg] or you'll lock up other nutrients.

yes that also i forgot to add check under the leaves if they have brown spots under its also a spider mite problem and if youre not giving your plant and cal/mag then this should dothe trick had the same probbut got to it before it got worse

ppl say not to use raid products even if its the kind for the garden but i said f u and did it anyways shit a guy gitta do what he gotta do but it works excellent and it gave no prob just spray 3 feet away but towards it and let it float its way