Hi Vanessa,
My husband Dan had 5-fu administered 2 weeks ago. He is on his second course of treatment and both times the 5-fu caused significant mouth sores followed by thrush in the week following treatment. He began taking a anti-fungal med last Mon. and slowly but surely it is healing. He was scheduled for 3 more weekly cisplatin treatments but this was put on hold until the thrush is cleared up. Side effects have a way of creeping up on you and I think all you can do is react as quickly as possible. It's a helpless feeling and both of you really need to have a cancer care team/provider that responds quickly and answers your questions and concerns.