5 Week Old Chick with leg paralysis and possible spasms

Today I found my 5 week old easter egger lying on her side in her pen. Until today she seemed to be thriving with her sisters with constant access to food, water and a source of heat. One of her legs seems to be completely unresponsive whist she can still move the other (although its pretty weak). She also seems to be breathing a little heavier and is yet to poop. I'm not sure if she's having spasms or if its an attempt to move herself. I haven't found any traces of distress or injuries on the bird and within her poo. She is eating some of her chick feed when I hold it to her and she's also had some sugar water. Recently I moved the chicks outside of the house onto the deck...this is the only real distress that I can think of the chicks going through in the past week. The chicks live in a pen which is covered on the top and bottom and has goof airflow. I use wood shavings which is cleaned out regularly. Today we had a warm day (32 degrees Celsius). The only real contaminant that I can think of is that the chicks tend to kick their bedding into their water which I clean out when I can. I've already checked over her for any ticks and other parasites. Any tips and possible diagnosis for my little bird would be greatly appreciated. There is a picture attached.