Veteran Grecians striker Jamie Cureton opened the scoring when he clipped a close-range shot past Chris Neal, before Danny Coles bundled in a second from two yards out in the 33rd minute.
Adams said: "It was a disappointing and frustrating night for us and I suppose we got what we deserved, nothing.
"We just didn't get going. We are a free-scoring side who have stopped scoring at the moment and the reason for that is we aren't getting into the right areas.
"At 2-0 down we had to chase the game and I made the three substitutions to try to find a spark, but I didn't get one.
"I thought Exeter worked harder than us and out-battled us and that doesn't agree with me too much.
"The biggest thing was the crowd stuck with us and what we have to do now is dust ourselves down, pick ourselves up and go again."