The workman that installed the fans was a Topologist!
An intoxicated Topoligist at that.
Wow. I have no idea why it would be like that. But if it were mine, I would take the two brackets in question, put them in a vice, and bend them the way they need to be. Problem solved. Although, since you have said that your neighbors have the same issue, you may want to trade first.
And I don’t know that the picture is necessarily crooked. It is hard to see in the picture and the camera angle is funny. You might want to double check so that RSSchen can sleep tonight.
The OP, I, David Simmons, Squink, Rhubarb, and Enright3 do. The brackets are made in two orientations, only one of which is used with any individual unit, and some fool mixed them up among several units.
Why do that when it’s much simpler to just swap blades?
Or problem caused, when the angles are different and cause vibration, or the cheap metal brackets break instead of bending.
Duh.
I vote against bracket bending. First, those are not easily malleable brackets and you face a high likelihood of simply snapping one or more of them. Second, it is unlikely that you will get a perfect match on the angle of attack, leading to a situation only marginally better than the current one.
I think the probability of multiple fans being dissassembled and re-assembled with confused parts is the most likely explanation of how it happened and simply exchanging blade brackets would be the best solution to solving the problem.
I’m really surprised that anyt manufacturer built brackets angling different directions.
In a later post the OP did say the fans looked old. The reversing switch is, I think, a relatively recent innovation and in the paST fans could have been made with blades set to throw air up or down depending on what the customer wanted.
The fans I put up back in the early 80’s all had reversing switches, so it’s not that recent.
“That recent” is a relative term. To me the early '80’s were yesterday. Unlsess you mean the 1880’s. 
Sorry, let me explain.
The light on the fan is the only light in my room, and it messed up the pictures when I took them with the light on. So I turned it off. In order to get high enough to take a good picture of the blades, I had to stand on my rolling swivel chair, that leans back, without any light whatsoever. :smack:
Sing it David.
Old equipment means pre WW II. The astronauts that landed on the moon have been kidnapped and replaced with old farts. It was not over 45 years ago that they did that. No way.
*:: Young whipper snappers got no clue about old… ::: sheesh ::: *