Confused?

My tank is about a little over a year old (the 55 gal) and my fiances tank is around 6-8 months old (the 45 gal) both our water parameters are good. Fish happy all good signs there. I just cant seem to understand why it is her tank always has a slight yellow like tinge to it and mine stays crystal clear. Even after water changes. Should i do a 50% water change on hers? Would that solve it? PS: i know the plants are quite overgrown i need to trim them up.