Mainly one plant, but kinda on some others too, maybe. That looks like potassium deficiency and some phosphorus deficiency too. Anytime there's a nute deficiency include calcium too. Hows the whole plant look?
that leaf is of the 1 not affected much the other plant looked good healthy as a couple days ago seems to have lost its dark green coulour and got those spots all over leaves i just started using pk 2nd week of flower
theres a couple pics the plant in the middle its hard to see the spots lights 3 1000de strains stawberry haze left ww x bb middle and afghan 1 right also rh was 17 lowest ive seen it usually about 47 rh
