2013 Prius C - Bulging Brake Lines

First off, many thanks to everyone on these forums for their knowledge, and apologies if this has been addressed elsewhere (couldn't find anything.)

TL;DR - brake lines are bulging and brake fluid is slowly disappearing.

Some relevant info: About a year, year and a half ago, I noticed my brake fluid was low (brake warning on intermittently, and then constant.) Filled it back up, no problems, went to get an oil change and they showed me that all 4 brake lines were bulging.

Tried to take it to dealer, but they had about a month wait for service, so I overnighted brake lines from NAPA and brought it to a Midas for replacement. I explained the issues to them, they looked and couldn't find anything. No issues for 6 months, brought it in for another oil change, same problem. Again, replaced (they ordered the parts this time) and they couldn't find anything that might be causing it.

It's now almost 6 months out again, and 2 days ago the brake light started intermittently coming on again, and I suspect it'll be the same thing. Has anyone else had this issue, and does anyone have any suggestions on the cause/fix?

Thanks!