tds/gh/kh/ph/temps are the usual criteria we look at when refering to water parameters. If the above is unknown, performing water changes really wont help address anything other than to dilute ammonia, nitrates and nitrides while bringing the onset of forced molts.
A lot of molting is not a good thing if you are not feeding sufficient calcium into the tank.
Lastly, you are forcing them to drop eggs each time you perform a water change due to a change in TDS. berried mommas cannot molt when carrying eggs so they will get dropped and spoil. Get a handle on your water parameters first and everything else will fall in line.
Should you not do water changes when shrimp are berried? Or do you just mean that the excessive water changes are causing the shrimp to drop the eggs, not water changes in general?