Spotted lower leaves

This is the first sign of long term excessive feeding...............it is not a cal/mag deficiency, it is burning.

Hi my friend, Seeing it like this, I’d say it’s getting too much nitrogen. I find it very green, even too dark. That’s the first thing that comes to mind. Have a lovely day.

I’d lean toward a calcium or magnesium deficiency. Your pH is okay, and I wouldn’t think it’s a fungus since your humidity and ventilation look pretty decent.