If you keep using a heated bed even with other filament types, there a couple of things you can do that might help. I think a lot of people try to start printing when the bed temp sensor is at the proper temperature, but the print surface of the bed is not. Cover the heated bed with a piece of cardboard or something else to act as an insulator while it heats up. That should help the heat soak throughout the bed instead of being lost to the cool room. If you have the slicer set to turn on the heat bed as part of a print, try turning on the heat bed manually some number of minutes earlier. This would also help allow heat to thoroughly soak through the bed, hopefully improving your first layer adhesion.