compatibility
 

does it matter if the rear derailleur, the front derailleur, the chainrings and the tube mounted shifters are different brands

thanks

If you have tube mounted levers, odds are that you don't have index shifting (though you might). For non-indexed (friction) shifting, mixing parts is perfectly OK, but if you have index the RD and levers have to match, and the number of gears on the levers must match those on your cassette.