I love wood chip mulch, and use a LOT of it. However, by adding a lot of mulch, you are dramatically changing the situation. If the blueberry bushes were thriving, I'd say leave well
enough alone. But, since they seem to be struggling, it might be time to act.
Mulch can simplify maintenance and add long-term nutrient, but look at mulch forums first and the troubles people have had with certain mulches in certain situations. I have found wood chip mulch to be great for perennials like blueberries, but consider your other plans for the space (will other plants suffer from slugs), as well your blueberry plants' potential susceptibility to voles. If your blueberries aren't thriving because voles are eating the
roots, you might be making the situation worse by adding a pile of mulch. And, if you don't already have a vole issue, you might be creating one - that is, assuming your region even has voles! :)
Maybe the best plan would be to test out a few solutions before making one big change. Mulch under some of the bushes, add nutrient under others (maybe worm castings?), add living ground covers under some (maybe alpine strawberries?), and do all of the above for another group. I wouldn't apply a big one-size-fits-all method right away, and I would definitely ask a
local blueberry expert before you do anything! If you put all your eggs in one basket, especially without knowing what works in your region, you could create bigger problems than you are solving. Your local extension service could be a big help with this!
By the way, if you want to connect, I'm always on Instagram with garden stuff:
@foodforestcardgame