...opened it up to about 90mph...
...jet trail?
Seriously: what air temps and humidity were present? Could it have been cold humid air creating condensate with the warm exhaust gases?
Or you had the bike only operated for a short time on a prior run, leaving a noticeable amount of dew in the silencers?
Fuel quality/water contend could as well be a factor.
(the cans of my 1100cc rig actually have drainage bores, dripping water out while warming up...)
