Q.Blueberry Plants Dying
I have planted 2 blueberry plants this year. However they seem to be forming red spots and rust colored leaves recently. I planted the blueberry bushes in Calloway’s Premium Tree and Shrub Soil (https://www.calloways.com/calloways-premium-tree-shrub-garden-soil). I also added some Azalea tone fertilizer to the mix. They were doing good for around a month and over the past week they have deteriorated. I’m guessing my soil isn’t correct for blueberrys. However I went with that particular soil because that’s what I was told to do at Calloways. Any insight would be greatly appreciated? I would like to replant some more blueberry bushes but want to make sure I have a better approach this time.

Certified GKH Gardening Expert
This looks more like infection from overwatering at the beginning. It is a good idea to keep them moist at the beginning, but they need to dry out just a little between waterings.
I would treat with a fungicide, and make sure to let the soil dry out, completely, down to 3 or 4 inches between waterings. Here are some articles that will help:
https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm
https://www.gardeningknowhow.com/edible/fruits/blueberries/growing-blueberry.htm
Another thing to consider will be the type of plant that you have. Some will not tolerate the heat, very well. There are a few that are meant for warm climates, though. This article will help: