Need help to detect deficiency

little early to be certain.. i'd guess k-deficiency. Got damage on serated tips and interveinal chlorosis. i'd let this progress a bit more unless you can be certain or other facts available to you that point to the same cause. Leaf symptoms are indiscrete.

Potassium problem

Yes, potassium deficiency.........scrubbyjimbob has offered you some good advice.

So looking at your diary, I see you've recently adjusted your nutes for an assumed nitrogen toxicity. You've stopped using the "grow" portion of the TA tripart series. The problem with that is by removing the "grow" you've also substantially lowered your potassium, the grows NPK is 3-1-6...it actually carries more potassium than nitrogen. Besides being important building blocks in the flowering stage, potassium and phosphorus play roles in the processing of calcium and magnesium. Think of it how sodium and potassium play complementary roles in humans in our electrolyte balance. I suggest returning to a more standard ratio on your base nutrients and in the future make adjustments to overall concentrations (aka EC/ppm) when tackling problems. Also before adjusting nutrients, do some runoff tests. Your initial "nitrogen toxicity" could have just been salts building in your media.