Fert burn or K deficiency?

[AnomanderRake]

That's still my answer. ^^^

Well, Biobizz say that you can use Biogrow every watering if you want...

About the light, I can tell it was a surprise for me. It's my first grow but here in my country I've seen a lot of peopple using it as the default for veg (HPS being the default for bloom). I will chek the ones you said out but do you think HQI light may be causing the problem with the leaves? In fact, only 2 of the plants are having this problem...

Thanks again!