Well thats the thing. Red stems can naturally occur when it's fall time and you've got outdoor plants and it frosts or is near frost. But they can also indicate nute lock, immobile nute, deficiencies..
Just based on my reading that is. Search the board for "red stems" and you'll see a dozen various things about it.

My room temp doesnt get below 68 that I've seen. High near 80. Humidity at 22% currently. Water temp at 70.

My brown spots first showed up when I was using tap water and treating it quite regular with H2O2 because I'd get a white froth in the water otherwise.

I've changed to RO water since then and using calmag.