Three Politburo members flew to the three Baltic republics Friday to deal with growing complaints that proposed Soviet constitutional reforms will crush current moves toward economic and cultural independence from Moscow. Politburo member Viktor Chebrikov traveled to Estonia, Vadim Medvedev to Latvia and Nikolai Slyunkov to Lithuania. Their visits were reported by state-owned media in the Baltics but not by the national media in Moscow. The visits come a day after the Politburo, the top Communist Party leadership, decided to consider changing draft constitutional amendments in response to thousands of suggestions, the official newspaper Pravda reported Friday for the first time.