Seems normal.. more bad players means more people to the flop and more sticking around so winrates will be a tad lower.

Btw I wouldn't necessarily try to adjust preflop, but rather postflop. Be less tricky, play draws passively (wait to see if they hit), bluff less. Don't be too bothered trying to put them on hands (which is futile vs loose cannons with massive ranges who can play any two when they feel like it) but rather discern their hand strength from their betting pattern. I really wouldn't tighten up preflop, playing more pots with bad players = good.