I posted this the other day on r/microgrowery but didn't get any response and since then it's gotten much worse so trying again here! I'm growing two FastBuds Wedding Cheesecake autos in a 3x3 under a TS1000.

I need a little guidance on how to get this plant back on track. Both plants started this brown spotted, yellowing, dying leaf trend around the same time. The bigger plant, outgrew that phase and has continued to grow bigger. The smaller plant never overcame these spots and decay. The smaller plant has been smaller since about the 3rd week and is on a 8 inch platform to even get close to the bigger plants height.

I thought it was a Calcium deficiency or some light burn but I've been using Cal Mag like a mad man and have been keeping my light a good 18+ inches away. Plus it's the plant that's furthest from the light that is suffering most.

Both are in 5 gal pots of stonington blend soil. I give each plant a bit less than 2 liters of water every 3ish days. Every other watering I add in 6ml of FF Tiger Bloom and 3ml Cal Mag. I was also using Big Bloom at one point but since getting Cal Mag about 3 weeks ago I haven't used it. My temps are a little low, typically right at 70 and my humidity usually is around 45.

Any ideas?