What is happening?

This just started two days ago and is spreading fast, was only on one plant and now it’s happening to another.
3x4 tent four plants under three qb 288 boards. Daytime temp about 75 and rh of 40
Night time temp is 60.
Ocean Forrest soil. Only fed with kelp and banana teas in flower

Phosphorus
http://catnews.org/FREE Pot Books/Marijuana Garden Saver [2005].pdf

kelp N n a few other things

bannanaa leaf P not to much others



understand ur plants needs or ur will die it's that simple

Thanks to both of you

I've been using the same FFOF soil for 10 months now. Kinda No-Till. Only feed organic nutes though to keep the microbes happy. My FFOF only lasted a 3-4 weeks originally before I had to start giving nutes.