Bitter mulberries - what's the culprit?

My usually productive mulberry tree has dutifully produced bountiful fruit this spring. I picked a couple cups today and has shocked at the poor flavor of the berries. Usually they are a beautiful mixture of sweet and tart, but today they are either nearly tasteless or just outright bitter. Very little sweetness or tartness and void of any actual "berry-ness".

Any thoughts on the cause?

I'm in central OK and we have been beset with a deluge of strong storms throughout the past month. 2" rainfall events have been common and our last 30 days has accounted for nearly half of our annual average rainfall. Is it possible that the flavor and sugar got diluted and only the bitterness was left?

I'm perplexed and saddened as I look forward to their appearance yearly.



ETA: this years crop is also smaller than normal at the ripe stage. Typically this tree produces fruit that is 3-4x long as they are wide. But this year's fruit is more proportional to small blackberries.