the time of year is most likely your issue. Is your male in a molt? Often fertility will drop a lot then, if not go away totally. Were they out at night before collection where they could have been exposed to freezing temps? That'll do it too.
I'm only getting 1-2 eggs a week right now off mine, it's just the wrong time of year for them is most likely the main problem. By March you should be in good shape. If not, then you may have to get a new rooster to go with them.
ETA:
Just kinda read over your post and wanted to ask one thing too. You said the first egg was laid over a month ago, and of the 12 none appear fertile. Just curious, how long did you collect them before putting in the incubator? Up to 7 days is fine, from there on it starts to effect it also. 14 days would be the max, beyond that, none would be much good. Just checking to cover all the bases.