Phosphorus deficiency or cooler night temps

These girls are about 3-4 weeks from harvest, the night temps have fallen down into the mid 60’s. One plant is starting to purple up on the main stem, down low and side branches starting to also purple. The other plants have purple spot where leaf fingers meet and one is starting to turn purple down that one leaf.

I know purple can be a sign of phosphorus deficiency, but it can also be because of cooler night temperatures. I have decided to top dress with coffee grounds but does anyone know the amount to use?



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I wouldn’t mess with anything. Your plants look healthy and the color your are noticing is coming from the colder temperatures.


Thank you!

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It could be a few things causing the purpling.
Cold temps can do it, but I don’t think 60’s is “cold”.
pH too high or low can do it
Magnesium deficiency (often because of pH)
Phosphorus deficiency (also because of pH)
Stress, humidity etc etc.

Where’s your pH at? Ppms?

The plant looks fairly healthy, and this close to harvest I wouldn’t get too drastic.