What is your humidity level at right now. You really need one of those cheap digital thermometer with humidity level display. I got one from walmart for like 10$. You can also mist the plants with water in a spray bottle a couple times a day to help them from the low humidity. Or get one of the small humidifiers. I started out using one of the ones that you can get for a kids bedroom.
You can buy a humidifier which can be kind of expensive, or you can start off by placing a bowl of water in your room and see if that helps. As it evaporates, it should help bring the humidity up. Also raising the temps a little can help, as long as they stay in the safe range.
i have a humidifier some place but i cant find it right now. i dont know what the levels are but im gonna go get a meter tonight from wally world. but for right now i have a wet towel and a bowl of water in there to try save them