Weeping Crabapple Redux

I was downtown around midday for a much-needed haircut (I hadn't had one during our European stay), and stopped by this weeping crabapple tree again.

Here it is three days ago--then the blossoms were pink, and now they are white, with no pink left at all. I don't recall having seen this behavior before, and I'm puzzled. Comments appreciated! (For the really curious I've pinpointed the exact location.)