My Mortgage Payment Decreased?

Last month I used the first of my new mortgage coupons--and paid about $50 less for my monthly payment.

I used the last of the old mortgage coupons back in September and kept waiting for the Bank of Oklahoma to send more. When they didn't I joked that I must be done paying my mortgage. Boy that was easy!

Of course, I knew I still needed to make my payments so I began trying to track down the person at BOK that could explain why I didn't get new payment tickets. I finally spoke to someone who claimed they sent new ones in February when my monthly payment had decreased. What?! I never got new coupons and I definitely wasn't aware my mortgage had decreased! How much easier would it have been if I had known that I could make smaller payments during months when money was a little tight?

This past year seems to be my year for financial mistakes though. During open enrollment for health care at work I realized (for the first time ALL YEAR) that my company has been taking $60 out of my paychecks instead of $6.25 for my FSA. But that money hasn't been going into my FSA. They reimbursed me in this last paycheck, but I feel like an idiot for not noticing months ago. And where was that money going anyway? What if I hadn't noticed?

Anyway, I finally got the new coupons. I'm still curious as to what would make my mortgage DEcrease though. I received a letter earlier this year that I thought said my home's value had doubled (the previous owner bought it for around $45,000 and sold it to me for $86,500), so I thought my taxes would increase. Of course the only things that might make that monthly payment change are changes in taxes, insurance or if I have a varying escrow (which I don't think I do).

Don't mistake me, I'm thrilled that I can make smaller monthly payments. Especially since I have a car payment now too. And it certainly didn't hurt me to be paying more than required. I'm just confused as to why my monthly payment would change. Anyone else have this happen before?