Yes, it is very odd. It sort of coincided with Maurice Whitman coming on board for the covers. And also coincided with the last sputters of the original FH titles. Planet issues #51-62 were bimonthly (through Sept. 1949), then #63 in Winter 1949, then #64 in Spring 1949. Then #65, arguably the first hyper-vibrant cover, appears with a "1951" date, and then very sporadically through the last issue, #73 (Winter 1953). Same thing basically occurred with Wings Comics and Fight Comics in terms of artist (Whitman) and sporadic output. Maybe FH decided the best way to save the ship was by amping up the colors, or maybe they bought a new printing press in an effort to re-energize. Or maybe they had money to burn (on flashy covers) to liquidate their assets and get some tax relief. Or maybe Maurice Whitman insisted on bright colors!
These are all completely unfounded hypotheses of course. But based on the erratic pub dates, it does seem like the company was teetering..