Millwall struck three goals in the second half and Huddersfield's woe was compounded by Jack Hunt's late red card.
"It was the last 25-30 minutes that killed us - we lost a bit of our discipline," Snodin said.
"In the first half it was fairly even and I think we felt a bit unlucky to be a goal down at half-time.
"But some of the players lost their discipline and we were pushed. They're upset but we've talked to them about it in the dressing room and we'll try to make sure it doesn't happen again.
"Jack was sent off for dissent. He felt he'd been fouled and the referee has sent him off for what he has said. In fairness, he's apologised to the rest of the players and put his hand up to that one.
"I think it's in the heat of the moment - we've all done it - but he recognise he's made a mistake.
"We've got a good team here but the last two away games have been disappointing. We've got a bit frustrated today because we were creating chances but nothing was quite dropping for us."