Are they retarded or are they doing this on purpose?

My stepdaughters are 13 & 14 years old and I seem to have to tell them to do their 1 chore everyday and how to do it everyday. I don't have to tell my 5 year to something but once and its done. When they are at their moms house they have to clean the entire house top to bottom so wouldn't you think our 1k sq ft apt would be a breeze cleaning only 1 room? Why do I constantly have to tell these girls to do the 1 chore I have for them (dishes in dishwasher & bathroom cleaned). I am to the point now where I feel like I am stooping to their level and said don't bother doing anything and from now on I'm going cook for you when I feel like it and see how that works out. I don't feel like I should have to keep asking you to do the same thing over and over everyday! My husband just talked to them today FINALLY about this and guess what after dinner came and went and no one cleaned the kitchen so at 12am I cleaned the kitchen myself again! Are they doing this on purpose or might they be retarded?