What age should girls know how to take care of their bodies?

I have 2 step daughters ages 7 and 9 (almost 10). Recently their father had to give them a hygiene talk because they went 5 days without a shower . They live with their mother full time and he gets them every other weekend and once during the week. He tries to tell his ex about the situation and she plays dumb. The girls are never showered when they come to stay and they can never remember the last time they took a shower. They are getting older now and their bodies are starting to change. I dont know what we can do to get them to realize that they need to shower atleast every other day if not every day.They dont even understand the importance of changeing their socks and underwear every day! This last time we had them they were wearing the same socks for 6 days and they were stinking up our house. We didn't realize that they were the same socks because they have identical socks at our house. We just figured they had stinky shoes and set them outside to get some air. What age do you think girls should know how to take care of their bodies and their own hygiene? I know that when i was 5 i would make my own bath and make sure i was clean and by the time i was their age i was showering every day without anyone telling me to ! I dont want them to be the stinky girls in their school. Dont you think they should know this stuff by now? Does anyone have any suggestions? I have already taken them to pick out soap and shampoo and smell good stuff and they use it when they come to our house. I have gotten them stuff to take home (little girly gift baskets). My husband and i have talked with them about how they need to take care of their bodies but it is like they cant grasp the importance of it all. Please help!
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Make a list of the things your kids are expected to do everyday & hang it up. When they want to play video games, play with friends, watch TV, etc say "Is everything checked off your list?" After a while they will have the things they need to do memorized and will do them automatically. For example, I would have something like. Daily Goals 1. Clean room 2. Do Homework 3. Read for 15 minutes. 4. Take shower. Just tell them the things on the list must be done every day before any fun activities occur. Also remember that kids that age may have trouble turning on/adjusting the water to a comfortable temperature, my daughter is 8 and I still have to do that part for her.
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