I had the same problem and on two plants I went from 2 to 5 gallon pots with well amended soil - blood, bone meal, and a few cups of dolomite lime - I made sure the PH started put around 7 so with normal rotting lowering the PH it finished in the correct range. Strangely, the stressed plants taste better than the super healthy ones. It was my first time but now I know my mistakes and will do better.
I bought plant lime in the plant section in the local Orchard Supply.
The ones I re potted resisted mold and bugs better and looked lovely right up to harvest and the buds were physiologically better and larger and actually finished vs me having to harvest other plants early because they all lost color and were battling to stay alive rather than thrive and make big pretty colas.

Good luck

El Gordo
eastbaygordo Reviewed by eastbaygordo on . ph runoff very low.. please help My pH going in is 6.3. Runoff pH is 4.9. I am using sunshine #4 mix & GH nutes. What should I do??? please help! Rating: 5