Problem on leaves ?

Thank you both for your answers. You guys are saying the same thing : not enough nutrient. In fact, I think I'm waiting too long between two watering. And I add nutrient one time out of 2. So today I watered them with 4ml/L BioGrow, 4ml/L BioBloom, 4ml/L Bio Heaven and 4ml/L TopMax. I'll wait a couple of day befere feeding them again and maybe I'll do the same again. I'm just scared to overfeed them. I read somewhere that I'm supposed to alternate water with nutrients and clear water. Isn't that right ?

Hey man! It’s looking like you either have some deficiency or lockout going on. Have you been religious about pH-ing? Flipping through the previous weeks of your grow it looks like it really started at the onset of flower, are you following a feeding schedule? Did you make any major changes to the light intensity that could be exacerbating stress? These are all the big things I can think of, most importantly I think is just pH because this does look pretty typical of an overall nutrient lockout. Good luck!