BSL..I dont think either master is bad. The rear is almost impossible to bleed without a vacum bleed tool...similarly for the front. It's rare for a master to go bad, really...if you do go on to replace it, I think you'll find the problem remains. A simple test..once you pump and develop pressure, does the lever remain relatively firm, or sink as it loses pressure? If it sinks rapidly, there is a probability it's bad..but if it remains firm or sinks slowly it's probably as I suggested, trapped air. Either way, before investing money in possibly unnecessary parts, why not borrow or buy a bleedtool... something you'll need at some point anyway.
The same goesfor the caliper...if anything, a sluggish piston will raise pressure not cause it to drop. If it's not leaking fluid then I doubt you'll find any benifit from replacing seals or pistons. Again, using a vacum bleeded will provide the answer to all questions and probably be the solution for the problems your'e experiencing.
Why am I so positive? Because I've been down the same road before. Got the same advice but ignored it[ naturally]...sad to report, after replacing many $$$ of unneeded parts, I bougt a 'MightVac'... never had a problem again...that was some 30 years ago.