You can't just look at the table average VP$IP and PFR, you need to look at the stats of individual players, and more importantly, how they react to you.

If you're normally pretty nitty, but the table is full of rocks and every time you raise you get blinds, it's time to start raising more hands. If you normally raise a lot of hands but there are two players to your left who call most of your raises and cont-bets, then it's time to tighten up.

If you're multitabling and aren't watching each table that carefully, just look at whether your current strategy is working. If it isn't and it's not just cold cards, you need to change it. If your current strategy isn't working and you have no idea why, it's probably best to change tables.