Clogged Line?

Have three toilets (1st, 2nd, 3rd floor). 3rd floor toilet functioning as expected. 2nd floor toilet has a Korky valve and always double flushes. I have adjusted the valve 1/2 dozen times (water level in tank) and either have a single flush (not enough water to clear toilet), or a double flush. 1st floor toilet seems to clog at a higher rate than it should. Should have I have my entire system cleaned/scraped/snaked/blown out? In the event this is YES, whats the best way? Snake, pressure, etc. I am going to replace the 2nd and 1st floor toilets anyway.

Thanks,

G