What are your soil/media temps? One time when I developed some rust spots ( after switching to flower) I was having nutrient issues it took me weeks to figure out my soil temps were to low causing the plants to develop magnesium deficiency plants struggle to absorb mag when soil temps are below 55ish deg…:usually when your plants have actual rust the rust spots are surrounded by yellow
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Cal-mag supplements with bottled fertilizer you’re using…
I cant remember which that is, i thought potassium when i saw first time.
I know that your bottle says like 2.5 ml- 5ml per gallon, this will PPM your water around 300-400 parts per million.
Your plants are developed and need more.
My mistake was more NPK
They need Cal-mag
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