Calling Stinky!! - Purple Stems?

I noticed today that the stalk and the stems are purple. Not solid dark on the main stem, but the usual color you see in pictures when people post up pics with this problem.

Plants had early PH problems. For some reason even after flushing my runoff PH was between 5.5-5.8. I always put in 6.8ph water.

I've transplanted two plants into 10" pots and left two in 6" pots as these were shorter and bushier.

Feeding twice a week with half strength Fox Farm Grow Big and Big Bloom.

I can't seem to figure this out. Water isn't too hard from the tap. I'm using Fafard Professional Potting Mix for the soil. No fert added soil....

Any ideas why I still get so low of a runoff PH and the purpling stems?

How are you testing the runoff ph, and exaculy what brand and type of soil are you using? Outdoor composts tend to be buffered to a lower ph than potting soil. :(

I've got a couple of non-purple (that I know of) strains that exhibit 'purpling' throughout growth cycle, and are fine otherwise. Some used to tell me it's from a phosphorous deficiency, but I use Phosphoric acid, so 'they' were wrong, lol. :jointsmile:

Any other symptoms?