Nathan Broadhead and Liam Delap had the visitors 2-0 ahead before Evanilson scored midway through the second-half.
Iraola admits they're failing to make clear-cut chances consistently.
He said: “I think we are five games without a win in the league, in games that I think we should have taken more points.
"When you are in a bad run, everything looks more difficult, more difficult to score. You need more chances, more volume and small things look like everything is happening against you.
“The minute they scored, the minute before we have Alex (Scott) against the keeper, they clear it over the line.
“The penalty that they call for us is the VAR outside, a little bit outside. Small things that probably when you are flying and everything looks easy, boom, there is a deflection, we score.
“Even to score today we needed finish, the save, the rebound, the second ball.
“It is not the clarity offensively that we've had in other moments of the season.”
Iraola also said, "I think we are not having the clarity now because today I think I've checked, we had 27 shots, and they have two shots on target.
“Obviously when you are playing in the opposition half, they have numbers, they defend well the box.
“The quality of the chances you have is not going to be very high because at the end they don't give you the space to attack.
“It's a matter of putting good crosses, finding good spots, but very tight inside the box.
“Shots from the edge. Even the shots we've had, we haven't been able to score. They blocked a lot and small things that don't make the opposition suffer, we need to get a lot.
“We're going to check the numbers, for sure, I haven't checked everything, the volume is there but it's not the clarity that we need to make the difference."