I have a Dirty mind about my husband and daughter.

This is a question not a make up, its probably been asked before, at what age should a dad stop bathing his daughter, our daughter is 14 and developing as a girl should with all the bulges and curves in the right places, in a morning we all shower, at weekend she has a bath before hand she sakes her dad to wash her back after she has been in the bath about ten minutes he goes up I didn't think anything at first but I started noticing the time and checking how long he was with her, it was between 15 and 25 minutes surely that's to long, I asked him why so long he said they were just talking, is this normal, I do have a dirty mind, I don't think this should be happening should I rock the boat.