PMS, Heavy on the P

Is it even possible for Avery and Reagan to be showing signs of PMS at six and three years of age??? A few days ago Reagan asked me for another candy. Because she had already had one candy I told her she could have no more because she already had one. She stormed out of the room while huffing, "That is what I hate about you mom!" I didn't even get a "mommy", just a "mom".
I make sure I get expilicit details every morning on what she wants for breakfast and I make sure that she chooses the bowl herself. If I am slow getting it to the table, she might change her mind and that will result in crying about not getting the correct cereal...after Avery and I just heard Reagan ask for that specific cereal. It is pretty funny to see the whole thing paly out.

Now for Avery, she too seems to hate me at the drop of a hat these days. I cleaned her room the other day,only to find it messy the following morning. Because we had a pretty busy day and company coming in the evening, I asked her to clean her room, get dressed and do it without whining (I added that last part because the whining started before I finished my request). After a few minutes of unproductive sobbing, I told her that if she doesn't do the three things that I asked her, she will not be spending the night at Nana and Papa's this weekend. We went through this same argument about four times. She didn't seem to hear a word I was saying butkept repeating,"I will do anything you say if I can spend the night, anything you say." I repeatedly told her that what she has to do is clean her room and get dressed without whining. After about a half hour and a few, "I hate you and I hate everything about my room." the room was clean, she was dressed and it was as if none of it ever took place.
Situations like these happen in our house on an hourly basis. Moodswings, perhaps??