Galvanized pipe corrodes from the inside out, so what might appear a decent line could be failing after 30 years. Dependent on location, the life span for galvanized is + or - 40 years. If your system is mostly galvy lines and you have witnessed a pressure drop in recent years, that is generally telling you your lines are corroding inside and filling lessening the inside diameter of the pipe, interrupting flow. Retrofitting w/ pex lines is common here where older homes used galvy water lines.

Unfortunately, since this has happened in two quite different locations, it's probably an early warning that the piping is failing and needs to be replaced throughout the house as well as the supply line from the meter to the house. Additional failures could cause more serious trouble, like slow leaking in pipes in walls that could cause rotting before you detect a leak; this may already be occurring. Although this is a little early for galvanized pipe to fail, you may live in an area where the characteristics of the water and its pH are causing a more aggressive deterioration than normal. Its going to cost a bit to have the piping replaced, but you can't keep continuing to do temporary repairs and hope for the best. At least get a plumber out to replace the failed sections as this will give you an opportunity to examine the pipe that's removed and come to some conclusions. I replaced my galvanized system at about the 40 year point, and it was so corroded with deposits inside that, when I tried to look down a 10' length of 3/4" supply line I'd removed, I couldn't see any light at the other end.

Kudzu9 right on with the mention of water pH.

99 of 100 people would never think that pH could have any relation to plumbing/fixture rot. PH< 7 = acidic; aka: aggressive water.