Magnesium deficiency?

Potassium, phosphorus, magnesium and a little nitrogen lockout by the looks of things.

If I were you, I would cut off all those brown leaves, because it can be contagious to other leaves and the plant will not focus its nutrients on those leaves. It could also be the nutrients or even the water, pH or nutrients that are too much or too little. Sometimes less is more. Do some small tests to see how it reacts. Good luck

Looks very much like phosphorus deficient. Hmm Also has hints of magnesium I'll admit. Magnesium is essential for photosynthesis, it is needed for the absorption of other vital nutrients. Especiall phosphorus. Magnesium is a carrier for phosphorus within plants. pH of your root zone may not be in the correct range, your cannabis cannot properly absorb magnesium through the roots. Often with this deficiency, the magnesium is present, but the roots cannot absorb the magnesium properly due to an improper pH. First you need to check as magnesium will have problems above 7 and below 5.

Hey there I agree with you it's starting relocate it's resources to make buds you can either uo your nutrients a bit or if your close to harvest just let it ride