Strange Lack of Flavor

I tasted my buch the other day to see if it was ready for 2F. Generally it is sweet or in that (for lack of a better word) sweet spot of sour goodness. The other day I tried my buch and on the back end where I would normally get the sourness it was flavorless, the first word that came to mind when I had it was flat (but not in relation to carbonation). Any idea whats up? It's been a few days so I'm going to try it again tonight.