I planted 5 blueberry plants this spring in the ground. We have clay soil, so I ammended the bed heavily, including the addition of sulfur to acidify it some. All plants are SHB. Three are fine, but my Southmoon and Sunshine Blue are having issues. I haven't checked the soil pH, but probably will need to. All are mulched with pine needles, and get watered 1-3x per week depending on the weather (we hit 100F yesterday). Any idea as to what the problem is?