Sure, some components will go off before others. It totally makes sense to replace one bath (e.g. CD is likely to go first and my local lab tells me that the pre-bleach# dies quickly in a processor tank) when other baths (bleach, fix) are still in good condition.

Trying to fix up the individual chemicals in one bath though is madness - unbaking a cake as pointed out above. Particularly because the chemical products of decomposition are chemically active and so merely replacing the missing parts will not restore you to the original bath effect.

# this is problematic because the chromes are handed over to the customer looking magnificent; they discolour in a couple of months and a whole bunch of customers get very angry.