Gavin Massey netted the U's second-half winner to make it back-to-back league wins against a cautious Vale side.
Adams said: "To be brutally honest, we were poor.
"I thought the enthusiasm for the game wasn't there for some reason.
"We started off with a system that didn't work and I'll put my hand up for that.
"Obviously I picked the wrong side, but I am really disappointed with the performance.
"I think that was as poor as I've seen us for a while.
"When we had seen Colchester down at Gillingham they had three centre-forwards who played really close together.
"So I thought I'd stifle that if I could, but it didn't work.
"Sometimes you try things but, to be honest, it was still 0-0 (when I changed formation) and we were still in the game.
"What I saw was disappointing.
"We were playing offsides and giving them time on the ball.
"Next week I will change the side.
"I don't want to go overboard, but it was a poor performance."
Colchester dominated early on, with Freddie Sears hitting the bar and Vale keeper Chris Neal denying both Massey and Sears.
Vale's Doug Loft went close with a half-volley but Sears' low shot flashed just wide after the break while at the other end, Chris Lines saw his effort fly narrowly past the woodwork.
Colchester eventually scored their all-important winner with 16 minutes to go when Massey converted from close range, after the impressive Neal had saved Ibehre's low shot with his legs.
- Sports & Recreation
- Gavin Massey