1996 330 Sundancer with strange white bloom substance in some interior seams ?

[Plane 2 Sea]

Had our beloved '96 Dancer for 7 yrs now. All of a sudden we are seeing some white, foamy like blooming substance under the stereo area in the horizontal seams of the different interior pieces. Approx.
1/2" dia., several areas. Doesn't seem to smell, wipes right up. Has stopped for now, but has reoccured several times. Any thoughts? May be humidity/temp related...