When you say it's off, do you mean a purple looks blue... or a brown looks maroon or are we splitting hairs and you are at 98 out of a 100 just not dead balls on ??
Some color manipulation just isn't possible and it will vary from profile to profile.
The very first thing I would do is find some common colors like reds, blues, browns and so on.... kinda like a Crayola crayon pack and print all the colors out and see which ones are off a little or entirely a different color. Next, instead of fixing it yet, go through all of your profiles with the matching media and see if they are all off the same in each of the profiles. We've had experiences of using the wrong profile with the wrong media and finding out, the colors weren't off, but the profiles were out of whack.
I don't know how true this is, but even using one brand of banner material will vary when using another manufacturers of the same stuff. Supposedly, they all have their own profiles.
After you figure out what is off, then if you want to calibrate everything go ahead, but there are still some other things you can do before calibrating your system.
Remember, if you're doing the artwork from scratch, you'll have a pretty good chance of everything working out. However, the vast majority of files come in from so many sources and regardless of how well your system is color calibrated for monitor to wide format printers to your desk top printer.... it won't mean squat if your customer sees a different color on their monitor. You can complain til you're blue in the face.... PMS 286, but if they give you something and in their heads it has to be PMS 280, you're always gonna be wrong.
There are programs out there which will in fact, print out the color you've chosen on your system and will print out about 100 or 200 close matches in all directions. This is by far the best way for someone to choose their color if they are finicky. We do it all the time.