The purple should clear up when you get your pH fixed. I see it on the petioles too now that you mention it. Micronutrient lockout, pretty simple, get your pH back in the 6.5-6.8 range and give those girlies a shot of micronutrient ferts. I just bought a product called algoflash I think the 'reviver' product.. micronutrient supplement... gave it to a couple palnts with that deficiency as a foliar spray... but you're in flower so you can only spray the lower leaves and CAREFULLY