M.B.
I would be honest in regards to her diaper area but also be "tackful". I would just let them know that when You were changing her today you noticed...a smell, redness, etc. and that you wanted to point it out to them so that the proper meds could be applied or maybe an appointment with her Dr. could be made if it continues. You might also ask how they feel about you giving her a bath to ease any soreness in the area. As far as "Spruing her up" that could be a more touchy subject.
I think it is up to you to be honest about how you have cared for her or any concerns you have regarding her during the time she is in your care! Just approach it as you would want to know if it were your child but make sure you deliver the information as want you have noticed and not what they aren't doing!
Good Luck!