Bluecrop Blueberry - Leaf Image Symptom Checker
So a little over a month ago I started 4 containers of Northern Highbush blueberry (in zone 8). Two are Bluecrop, one is Darrow, the other is Spartan (I'm aware I'm in zone 8 and asking for trouble with Northern varieties). They were potted in a premixed "Acid Potting Mix," and are mulched with redwood. None have really taken off. But now recently all of their leaves are starting to turn red.
Checking their PH gave me an alkaline reading of about 7. After seeing their condition decline, I just yesterday repotted them all and amended the soil with cottonseed meal and sulfur.
The provided image of the top of the leaf is extreme, and not typical (yet), and I suspect might be a fertilizer burn, but the image of the underside of the leaf is what most of the outside of all of the leaves on all of the plants look like. From Northern Highbush Blueberry (Bluecrop) Disease From Northern Highbush Blueberry (Bluecrop) Disease