Potted Blueberries, reddish leaves
I have four potted dwarf blueberries that I bought last year (two tophats and two northskys). I fought most of the year to get the right soil acidity, and had the leaves slowly turn red while the ph was too high. I finally repotted them into a soil mix specifically for blueberries, and they all came back. They overwintered in the garage, and all came back this spring looking quite healthy.
But now I'm getting the leaves slowly turning red again. It's worse on the tophats but the northskys are also showing it. I did a store bought soil ph test and nutrient test. The ph was a bit high but around 6 which I don't think is high enough to cause this. I'm mixing some sulfur into the top 4 inches of soil to see if I can't bring it lower.
Nutrient wise, nitrogen showed very high, phospherous was moderate, but the potassium was next to non-existent.
I'm not sure how much to trust these store bought self test kits, but would potassium deficiency cause the leaves to lose green and start turning red? I haven't fertilized them yet this year since they started to flower and I thought I shouldn't feed while they're flowering.