My uncle had some similar looking sad blueberry plants. He ended up speaking with a master gardener at a home/garden show of some sort and he suggested mulching with pine bark to help get the soil to properly acidic.
Thinking about it, I'm pretty sure this should help. I used to live in Florida, and the local state park had a certain trail through some pine forest. There were wild blueberries growing all through that area along the trail where the canopy was thinner. They seemed to be thriving there, and the main characteristics of the place were partial shade, well draining soil (Florida soil is super sandy), and natural pine mulch from being under pine trees.