Not only would I suggest that you stick with the 5-1-1 mix, especially if your plants are healthy and happy, I'd go so far as to say that a repot probably isn't even strictly necessary at this point. Here's why: fabric pots function more like raised beds than containers (that is, as long as they're in direct contact with the ground/soil). That means that, even if your mix has compacted as it has broken down, your fabric pots won't support a perched water table in the same way that plastic will. Also, fabric pots encourage branching rather than circling roots, which helps to prevent plants from becoming root bound (or at least slows the process down). Furthermore, blueberries' fine, net-like root systems aren't all that prone to circling anyway (or, at least, that's been my experience), so the combination of fabric pot + blueberry gives you more latitude than you'd have with other plants and pots. That's not say that root maintenance is a bad idea, especially if you noticed any signs of flagging growth or stagnation. Rather, I'm merely suggesting that it's not necessarily a "must do" at this point. However, if you do decide to bare root and repot them, then I'd stick with the 5-1-1 mix or something similar. If you want a mix that's suitable for fabric pots and that will also hold its structure longer term, then I think I recall Al recently recommending something like 3 parts screened park to 2 parts turface. I haven't tried it, but I suspect that the standard gritty mix would drain too well and dry out too quickly in fabric pots.

Blueberries love peat and bark. If in gritty mix PH is now more of a concern. Blueberries love to be moist, it's hard to overwater them. I would stick with the 5-1-1. I myself use a 1-2-1 mix with diatomaceous earth instead of perlite. DE holds more water. I have three blueberries in this mix. Excellent results so far.