It's not clear to me what part of the display you are talking about, so I'll choose the yellow Manoeuvre Margin. This is set on the FMC MAINTenance pages under PERFormance Factors.
The monthly Nav Database updates can reset some of the parameters on the PERF FACTORS page. As the problem is fleetwide, I suspect this is your problem. BTW, what is your normal manoeuvre margin... 1.2? 1.3? Or something else?
Please let us know how you go.
Rgds.
Q.