Oral minoxadil and hair color

Hi! I did a color consultation for a woman who is having a hard time keeping black hair color in her hair for longer than a few weeks. I did a test strand with joico which isn’t what I normally use but have it for one client that likes that raven black hair. While that processed we talked about her habits and the possibility of mineral build up from her water and when I asked about medications she mentioned taking oral minoxidil (I didn’t know that was a thing). I did a quick google search and read it could cause hair to go darker or lighter. I’m wondering if this may be what’s causing the color to fall out so quickly and want to ask if anyone else has experienced this. Our plan is to wait two weeks to see how the test strand holds up and if there’s an issue we will do some Malibu treatments and then try an all over color.