Dahlia blooms didn't last when cut this year. Any ideas why?

I've been growing dahlias for many years with wonderful success. I'm a lurker, and depend often on the expertise I find here. I moved to a new house 4 years ago and have had little success with my dahlias here. Finally had a soil test done - hard to admit I couldn't fix it myself, call me stubborn -- applied the recommended soil ammendments, and had spectacular dahlias again this year!! Life is good again!! Ahhhhhh .......
Almost ..... I love to cut the blooms and share them. But the blooms wouldn't last more than a few days, not a "week" like they've always done before.
Any ideas what could cause this? I put the additives in the soil several months before the dahlias went in, well before the spring rains last year. I'm in zone 6.

Mine have never lasted a week so you're far ahead of me!

There were some that didn't last that long, but some of my oldest friends like Kelvin Floodlight, Thomas Edison, Otto's Thrill, and one of my favorites, Caribbean Fantasy, would last and last, especially if I gave them their special little tonic -- equal parts lemon lime soda and water, and a few drops of bleach. But this year, even that didn't seem to help. They started to wilt almost immediately and with few exceptions, had drooped completely over 2-3 days. Many of the places I take them, I take them once a week and used to have to replace the old blooms with the new ones, or someone would take the old ones home to enjoy for a few more days. They really did last that long.
I was just hoping someone else had experienced something like this and had some advice for me. I watered when we didn't have rain, and besides the soil ammendments, treated them as I always have. They were very late blooming. I start them in pots, and had them in by mid May, but had few blooms till mid to late August. Had a gorgeous fall though.
I've grown dahlias for about 15 years, and learned by trial and error. Bless their big old hearts, they have forgiven me a lot over the years! And they still amaze me.

I am trying this lemon-lime magical recipe you speak of. If I get three days on a bloom I consider myself lucky.