Leaves are changing quickly, yellow w/ brown spots - first grow - Help!

Hello everyone, I come here and read - a bunch - and digest as much as I can. Well so far so good with ILGMs Gold Leaf Autoflower. They are about 7 weeks now and just started flowering. They are in a 4’x4’ w/ a Mars Hydro 2000. I have been feeding with FF Trio as recommended 1/2 strength and also using CAL-MAG. The lights are on a 18/6 schedule and is about 12-15 inches above plants.
This condition only started showing up about 10 days ago on one plant and now is on a ssecond Please take a look at the pictures and let me know what you think. I only see this on older leaves. Not at all on new growth. All the new leaves are fine.
As I mentioned I have been here reading and these plants got way ahead of my knowledge. I feel like I am always two or three weeks behind them. Thanks up front for the help I know will come. This is the first time growing myself. I’m retired
and have always had large gardens but this has been an adventure . More science than I have ever applied before. Looking forward to learning more .








What’s your ph

Hello…I have been keeping the watering at 5.91 at the lowest and 6.29 or 6.48 once as a high in second to last watering.

What kind of soil you using

Another thing might want to defoliate a little on the bottom half for more air and light

Yah i would defoliate ur plant so u mite be able to get rid of those leaves that are damage but in saying this u mite want to give ur plants a dose of cal/mag when u water again

Ya trimm them up a lil n give them a dose of cal mag i think that should clear them up growmie. Good growing !!

This is what I have been using. PRO-MIX BX Mycorrhizae Growing Mix. I have used it before for other plantings and it was on hand. It seems to work well. It drains well. So far zero problems with any bugs.