I suggest a compromise pruning. Instead of cutting them way back to get rid of the spotted foliage do some selective pruning by removing only the branch tips most affected. This way you can still enjoy a harvest because you are not cutting off all the blooming tips. From the image you posted, I am not positive your shrubs have rust. Could be winter damage. A light pruning along with a mulch on top of the soil will kickstart the plants to push out new growth. If you have not fertilized with a plant food for acid loving plants, apply fertilizer at the base of the plants before you add the mulch. Your blueberries may grow out of these spots and if not, you can always try the drastic pruning early next spring. Keep growing, Marianne Binetti