Jake Wright’s seventh goal of the season handed the Pilgrims the lead on the stroke of half-time.
But Simon Richman equalised for the hosts with 20 minutes to play before Jacob Blyth’s flying header won it 12 minutes from time.
“We were in total control in the first half,” he said. “We should have scored more than one goal.
“The goal was a superb move and full credit there, but to go from that to what we did in the second half is not acceptable.
“It is down to me and I take full responsibility.
“I thought we would have learned from Tamworth and we haven't learned. That was clear and evident in that second half.
“The distance of the ball coming in for the second goal was too far. We have got three defenders in and around the ball and they have one attacker and have scored, it's not acceptable.”
Culverhouse is now vowing to work hard on the training ground in the coming week.
He has also signalled his desire to bring in some fresh faces.
“We moved it really well in the first half and looked a proper side,” he said. “This (result) is down to me and I have to do something about it.
“That’s twice on the trot we have got involved in a brawl. They bullied us in the second half and it's not acceptable.
“Balls in our box are coming in too easily and we are not being aggressive in our own box.
“Games are won in both boxes and we are not good enough at defending our own at the moment.
“I have to do something and we will work hard this week to rectify what is going on.
“We will give people chances but I think we need a couple in. It is my fault and I have to do something.”
Loan defender Tom Nixon added: “We dominated the first half and took control of the game, but in the second half we didn't seem up for it and they were, the result shows that.
“The first half was class and we played the way we play, but it seemed that everything changed in the second and we didn't stick to how we play.
“I have really enjoyed my time here and I hope to extend my loan.”