Never saw it before. Never had it. I don't know. There hasn't been any sign here of bberry health issues. The top photo had me thinking of water damage -- rain on the leaves when the hot sun came out. Droplets work like a magnifying glass on the leaves.
Most leaf diseases I have checked out for blueberries tend to look like round spots when they first start to show. Any chance that it could be water stress?
It looks like new growth...mostly? Or is it all over the bush?