advanced nutrients ph perfect

Hey everyone, I started a closet grow couple weeks ago four different autoflowers from RQS, 2 Royal Runtz Auto, 1 Cookies Gelato Auto, 1 Purp Punch Auto. I've having trouble with the pH of my growing medium, I'm using 50% Coco 50% soil. Testing high alkalinity around 7.5-8.0, My seedlings are on...