My blueberries did well where they are for several years. Now some, not all, are turning yellow about midsummer and by late summer the affected bushes are dead. What must I do to correct this? Thank you.
The first thing to do if you're having problems with blueberries is to get a soil test, to make sure they have the pH and nutrient conditions they need. This article has basic information: https://www.gardeningknowhow.com/edible/fruits/blueberries/blueberry-fertilizer.htm
Then check the area where the affected bushes are (or were;) is the area low, or shaded, or is something affecting the drainage in those spots? Then look at leaves and roots for signs of disease or insects. Here's an article on diagnosing blueberry problems: https://extension.psu.edu/plants/gardening/fphg/blueberries/diseases
The county extension service might be able to help you identify problems, probably if another bush starts to fail. This link will help you find the nearest office: