The problem is that if you were to set the decay to one day, like you did, all future events should decay as well. Disabling decay undoes the decay (as the systems can switch back and forth between each).
AT this point, your best bet is to run a Mass Adjustment and give everyone the appropriate negative adjustments to get them where you want them to go. At the moment, there's no way yet to do an automatic X% reduction of everyone's totals.
I see, thanks for your help. The only thing is, it has been working perfectly fine for the past 5 weeks. Is there a reason this problem has chosen to manifest itself now?
For a few weeks, the decay wasn't calculating at all. For most guilds, this amount isn't very big, which is why it took so long to notice.
But when it was fixed to run, the difference was huge and that's why everything seemed to be normal. New raids weren't decaying for you like they should have been.