I had one gut string which faded to a yellow-ish color on my pedal harp. Only a few weeks later it broke. I had no idea why and it was only one string, now that it’s been replaced it hasn’t happened again.
Perhaps ordering another set of strings? But as Tayce said below, if the sound is good does it matter? I have no idea what would cause the strings to yellow, in my case my harp is also completely away from the sun and none of the other strings changed so I don’t think it could be light exposure! I hope you find a solution!
— Natalie