Strawberries have a short fruitful life. They reduce the amount of fruits the older they get. By the time they are 3 yrs old, the yield will be minimal. The grubs could be the larvae of the dreaded vine weevil, a real pest of strawberry plants. I Don't know about the red dust, but someone else might be able to comment. Personally, I would discard the plants and start again. But don't be too upset, they probably would not have given the quantity or quality of last year.