Do NOT bring your water pH to 5.5-6.5! The correct pH for potting soils is 6.5-6.9, and soilless 6.3-6.6.
Looks like low soil pH causing lockout and rootbound causing crappy soil chem.
Is that a pot with a built-in catch tray?
Get it off and check your runoff pH. Also slide the plant out when the root ball is dry and look at the roots.
I foliar feed with GH Micro while I am trying to solve these sorts of things, to bypass the roots and allow feeding to continue while the problem is sorted.

You may be ready for a re-pot. Either way, I'd do it- your soil chem is off and needs fixin'. Flush @ 6.9, feed lightly @ 6.9, allow to dry, re-pot into fresh light soil in a slightly larger pot.
stinkyattic Reviewed by stinkyattic on . Mums Sick?? As you can tell, I have been topping the shit outta these girls to be good mums. The have not received any extra nutes yet.Just water, and the FFoF, Roots, and seed starting soil mix, (end of the bags), and about 30% perlite. Now the ladies are about 7-8 in tall, and MANY side branches/clone sites. Well now, half of them are going completely purple on the stems, stalk and starting to go into the leaf veins.HELP!!!!! Dont see how rootbound can be an issue on such small plants in 1 gal Rating: 5