Rangers slumped to a shock 2-1 home defeat against Annan on Saturday and Ally McCoist's side have now conceded goals in their last five Irn-Bru Third Division games.
Alexander is one of the longest serving players at Ibrox and he is worried that the Gers have let their defensive standards slip this season.
"We are giving the opposition chances right, left and centre and we are conceding goals that in years gone by we would not have conceded," he said.
"It's a head-scratcher. What are we doing differently? What are we not doing right? So that's why we will work hard in training, we will watch videos and make sure we change things and cut these things out.
"The thing is we need to score at least twice in matches to win games because we are conceding and teams gone by didn't have to do that."
Rangers remain 17 points clear at the top of the table but Alexander has urged his team-mates to remain focused until the title is secured.
"Sometimes complacency creeps in - although I would like to think it didn't. We are so far ahead and it is virtually job done but we are not over the line yet," he said.
"We have a fairly inexperienced team in terms of winning championships and we all know that last Saturday was not good enough from start to finish.
"It's not acceptable for Rangers players to perform like that but hopefully we can win this weekend, things will be forgotten and we can move one step closer to winning the league."