Goals from Simeon Jackson and Dennis Oli secured three points for the Gills, who remain among the play-off places as they look for a swift return to League One.
"We have just got to keep battling. We are in a precarious position now and we have to get out of it," Coleman said.
"It is our lack of goals which is killing us. They scored two deflected goals and things drop for you when you are at the top but not when you are near the bottom. We gifted them the goals and I think the scoreline was harsh on us.
"The lads are dejected in there but we have to pick them up now. We are working hard, the effort and work-rate is there but we are just lacking quality at the moment. We need to be more ruthless in front of goal.
"But I am no quitter and the players aren't and we will keep going to get ourselves out of this and hope we can."