Hello Tikva!! Welcome to the forum. Winter time can be a tough one for keeping the humidity up (and for me I live in a not so well insulated building formerly a mill!). Anyway, for me I keep my humidity trays full at all times and I keep them fairly close together to keep the localised humidity up. I also have a humidifier that I fill at least twice a day (once before work and once when I get home). Another way to keep your humidity up is to take sheets of plastic, and hang them up in your growing area making a tent around them, but watch out for stale air that could lead to mold, a small fan is real useful.
So, what else are you growing besides the Masd. 'Celtic Frost'? Where in NH are you?