The Gulls are falling like a stone after their eighth defeat in nine games and only a couple of brilliant Michael Poke saves from James Constable and Alfie Potter kept them on terms in the first half.
Some of their defending in the second was worrying as the visitors ran out 3-1 winners.
"A straight ball between our two centre-halves and their forward goes through to score for the first," said Gulls boss Knill, who introduced new loan signing Joss Labadie from Notts County in midfield.
"And for the second one Aaron Downes should have put it into the stand, decides to do something else and it's a penalty.
"Two goals in less than five minutes have killed us. I thought we were OK at times in the first half, but I haven't seen us put a whole game together yet.
"I thought Joss did quite well, and he'll be a good addition for us, but he got cramp near the end and we had to take him off.
"We can't blame anybody but ourselves, and we're the only people who can put it right. It's plainly obvious that the players are edgy at home, but we have to be better."