Hey 3Derek7, maybe (from your description it sounds like it could be), changing tubes is always a good place to start. Do you know the history of the tubes in your MP1 (IIRC ADA recommended MP1 tube change every 2 years but is in the manual (see MP1 area), I assume this was based on very regular use ~3 to 5 night per/week). Anyway it's a bit academic, if your tubes go off, you should change them. For example, MJMP changes the tubes in his MP1 3TM every month or so, a bit like guitar strings (albeit a little longer, when I'm giging I'll change strings after every 2nd gig), but he likes to keep them at their absolute peak, which I understand (he doesn't throw them away, just puts them into other gadgets as they are not dead, probably just lost that "new" sparkle).
I've had MP1 now MP2 for many years, I only changed the tubes in them once each. The original Chinese tubes punched well above their weight and lasted a long time.
So take off the lid and check the tubes. The original tubes have no brand just say 12Ax7 in red. And while you've got the lid off put in 2 new tubes (my current personal favs http://www.dougstubes.com/preamp-tubes/12ax7-ecc83-7025/mullard-12ax7.html) or (the short plate version http://www.dougstubes.com/preamp-tubes/12ax7-ecc83-7025/mullard-cv4004-12ax7.html) either will melt you and work well in MP1, (or if it still sounds bad there's something else wrong so let us know how you go).
It may not be tubes BTW (as I said new tubes can't hurt and it's probably high time for some), tubes tend to go off slowly over time (newer tubes faster than the older tubes (mostly coz less vacuum/pumping these days)). But they tend to just not sound quite as good, not necessarily quite what you describe. Change out the tubes (you probably need to anyway) and we'll go from there.
Cheers Richard