Article 3-4 Purple Plants

My plants stems are quite purple in color, they are four weeks into flowering and appear to have stopped growing. Most of the larger leaves are yellowed, dried up and fallen off. This is the first time this has happened with my plants which are normally healthy. Can you help or suggest anything I can do for them? Thank You
Sad Plants

Sad Plants: If this variety does not normally turn purple, the following are likely suspect: Note: On an eight week cycle you should expect less than average yields, even if remedied, as the plants are going late into their life cycle.

  • Anthocyanin pigments (leaf coloration) often develop from cool temperatures, this includes the roots. Take measurement of root and air temperatures, both during light and dark hours. In soil, it is usually 10° cooler than in air.
  • Phosphorous, required for blooms, fruits, and flowers might be deficient. This could be a pH related problem, check the pH at the roots, not the solution. Also make sure that you are adding sufficient amounts from your fertilizer. Phosphorous also becomes deficient at temperatures less than 65° Fahrenheit at the roots for extended periods.

A quick foliar spray of mono-potassium phosphate with a B-1 solution will provide a little relief, but this will not fix the problem. Be sure that the area is well ventilated and the lights have been raised, to avoid powdery mildew on the developing flowers, and to prevent leaf scorch. Test the spray solution on a couple of your plants before spraying them all.
Erik Biksa