Oily Maltese Hair

Question
I have three Maltese.  The hair of just one of them gets a very "greasy" look to it within 5-6 days of being groomed.  I used a high quality washing product at home in between professional grooming. Can you tell me how to help this situation?

Answer
I commend you on being such a good dog mom by keeping up between professional visits!
Welcome to a problem professionals deal with on a regular basis. Your dog has a different ph than the other 2. It is not uncommon.  So what to do.
Try a different shampoo- medicated perhaps, Dermaplex, nothing too strong and without a conditioner, just on this dog. Some dogs just need to be bathed more. Which in your case sounds like a possibility, as long as there are no underlying health issues. I have a dog we like to bathe every 5 days she gets so greasy. I know it's extra work but like children some dogs demand more attention than others.
Sorry I can't be more helpful, but there are no magic bullets on this.
Diet, exercise, stress, pack order all contribute to the quandary. You may want to research these as well.
You should also discuss this with your groomer and see what they are using on the dog at the salon.
good luck