The visitors remain undefeated in the capital in the Clydesdale Bank Premier League this season after strikes from Ross Draper and Andrew Shinnie, either side of a deflected Leigh Griffiths goal, were enough to secure the points.
The defeat leaves Hibs in the bottom six with a trip to Celtic Park their remaining fixture.
"I don't think the result was fair," Fenlon said. "Maybe we didn't deserve to win but I certainly don't think we deserved to lose. I thought the work-rate was tremendous.
"We had a great opportunity to get a home win and put some pressure on the teams around us and I'm disappointed we haven't done that.
"We gave away two sloppy goals. The first one we didn't defend a straight ball and then with the second goal we defended the free-kick well, but didn't win the second ball. It's not rocket science.
"The desire not to concede sloppy goals is something we want to get into the team. We need to make teams work harder to score against us."