In run mousses which are supposed to be about 15 psi but I think once they've been used a bit it's more like 12 psi. Oh if only we had problems with it being dry and dusty! Rain, rain, rain, grey, grey, grey that's what we've had for months now.
Undoubtedly if you can run lower pressure you'll get more grip but have you checked riding style hasn't slipped? If I do a lot of trail riding I find I get lazy and then when I do an event I struggle to find grip as I'm not so used to caring about getting the most out of everything.
When I used to use tubes I would run down to 12 psi front and 10 psi rear if short of grip, but no lower and that assumed it either wasn't rocky or I had time to pick my way throught. I have run trials rears right down to 6 psi as they are much higher profile.