Brown marks in leaves.

Hey buddy. Just by looking at your plant I can tell what you are experiencing is nute lock now due to your N tox. With soil, which light mix is. You should only feed once a week and then water for the rest of the week. What's happened here is you slowly built up N and your soil/plant have built up with salt and is now going through a nute lock out, the N tox hasn't gone too far cause if so that leaf wouldn't be experiencing nute lock. You need to do a hard flush. I don't like flushes or any run-off with soil but if you have been giving feeds every time your soil in toxic. Flush and give her a week. Just add just cal after flush so the plant can take up what nutes are left in the soil then restart your nute programme at 1/2-1/3 the strength for the 1st week and then go back up. But with soil you HAVE TO give water inbetween to flush out excess salt and nute build up....now when I say flush...don't think that means you need to get run-off. It just means the water is coming behind your feed to flush the soil. Good luck feel free to DM me for a more detailed feeding table if you want. Happy growing.