be slow off the mark
To be slow to react or take action. He's too slow off the mark to be an effective emergency responder. You were a little slow off the mark on your last line. Come in a little bit sooner next time.
be ˌquick/ˌslow off the ˈmark
be quick/slow to do something or understand something: You have to be quick off the mark when you answer a newspaper advertisement for an apartment.Jenny was rather slow off the mark, and they had to explain the joke to her.In athletics, your mark is your starting point in a race.