second for older

Hi Everyone. My introduction to Brittanys was by adopting a rescue dog from Spain. She has been with us for 4 years now and is 9 years old. We love her dearly. She has a great temperament and quickly got used to being house-trained, living inside and loves being part of a family. We think she had been used for puppy production. My query is that she seems to have brown "tear tracks" below her eyes. She does not have an eye infection. Can any one of you lovely experts give me some advice on how to clean these. I just don't seem able to clean her effectively. We split our time between Spain and the Isle of Man. TIA. second for older