Ross Draper and Andrew Shinnie scored either side of a Leigh Griffiths goal to give the visitors the three points but Fenlon thinks his side can count themselves unlucky.
And the defeat leaves Hibs eighth in the table, with a trip to Celtic their only remaining fixture before the league splits in two.
"I don't think the result was fair," said Fenlon. "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."