My potted Sharpblue blueberry bush looked moderately healthy up until today. Just yesterday I added a conservative amount of Espoma Soil Acidifier as part of a schedule (April through July) and overnight the leaves went paler and wilted. The weather has been average and I did not over-water. I did a quick Soil Master pH test, but I do not trust the results. It read around 7.5, but it was previously lower and the plant was doing fine until today.

Any ideas what is going on?