Weekend from HELL

So sometime on Friday around 6pm my girls turned into monsters. And basically didn't stop until later afternoon on Sunday. First the middle one had worn shoes to school that hurt her feet and gave her blisters (don't get me started on the reasons why). So when we went to the pool Friday night she screamed when she got in the water, cuz her feet hurt. And continued to cry pretty much the entire time we were there, because she wanted to go in the water, but couldn't cuz it made her feet hurt. Then when she and her big sister asked for snacks I said they could have rice cakes (they love them) - three of them. They wanted candy also. I said no. Then big sister said she didn't only want 3, she wanted 5. I told her three or none. She kept it up, so I took them away. She lost it in a screaming fighting match through when we came home. Saturday they didn't want to nap. I told the big one she could lie in bed next to her little sister until she fell asleep and then she could go to our room and watch noggin. Instead, 45 minutes later I go upstairs and they are both watching TV in our room. I ask big sister if little sister had fallen asleep, but then woken up and joined her, and she says no. They both lose all tv for a week, prompting massive meltdowns by both. Little sister actually went completely hysterical (she also forfeited her love toy in the middle of the mess) for over an hour before completely exhausting herself and falling asleep. Then today they pull the same thing with not wanting to nap and are just generally pretty whiny all day. It is something in the air? It better not be the humidity, cuz we are just at the start of that!