...was that soil from the bag? If so, it's not relevant now this far into the grow, too many other pH influencing factors once in-pot! Still, it does tell you the soil is acidifying,...
What nutes are these? bloom nutes with those NPK #'s is weird, too much N, not enough P,...
yeah, you can pH adjust your inputs to 6.8-ish, to help raise things up some,... may take a few applications along with more P,... I'd say you should try a different bloom nute too, something with large P-K numbers, higher than the N value,...