Navy Mum On Ships’ Destination- Tuesday, Jane INavy spokesman continued silent today on published reports that six ships left the Naval Base yesterday, reportedly for duty off the coast of Vietnam as part of this country's buildup in Southeast Ada.Sources have said—the following ships left for Vietnam; the guided missile frigate Dewey, dve destroyer Davis, and destroyer escorts Bowen, Page, Trippe and Joseph Hewes,All but Page are from Squadron 20. The Page b from Squadron 12. The deployment affects about 1,600 men, ■A Navy source In Washington said the normal deployment for ships in Vietnam U six months.A spokesman here said accounts of the deployment are • “not completely correct, but he declined further comment.Two Newport-based destroyers Myles C. Fox and Cecil already are on duty off Vietnam. They were the first Atlantic Fleet ships to arrive In the western Pacific since the recent buildup In the war.