The NL starts developing yellow leaves at the top ...

Creo que tiene razón Robert! La luz está muy cerca de las puntas y lo primero que hace es ponerse amarilla, luego aparece la necrosis y finalmente las puntas se empiezan a quemar como si estuvieras sobrefertilizando

Yellowing leaves on the top of the plant point to phosphorus or potassium excess, but it could just as easily be light burn. I noticed in your diary that your led light is 8 inches away and you don’t say anything about temperature or humidity. I would recommend raising your light some and give her a few days. Check your environment, ph, nutrient levels, make sure everything is on track. Sometimes a quick flush to reset things can help, followed by a half dose of nutrients. Good luck!

It is light burn. 8 inches is too close. If these guys would stop and look at the information in a diary vs googling a answer they would see it is a very obvious answer. Took less then 30 seconds.

new blades look thin with interveinal chlorosis.. could be p or k tox. kinda common with the way some of these brands instruct dosing during flower phase... use what infor you have to eliminate possibilities.. what is given here is not enough to give you an answer with any confidence. consider how you've fed lately.. any changes you've made to formula etc... go back 2-3 weeks even.