The only thing that concerns me is that squiggles sneezes a lot. She would sneeze before here and there but now it's like every minute, sometimes more, not when she naps thought. I read some threads and for most of them it just resolved on it's own so I'm not panicking. Yet.
Look forward to the photos to see what you are talking about.Also her back fluff is nowhere to be found. The other two as they grow their backs stay fluffy with the baby feathers but squiggles has like this bold patch where I can see the skin on her back and legs.
Do you see the others picking at her fluff?
Has sneezing increased since you added the Hemp bedding? Sometimes sneezing is environmental (dusty bedding, dusty feed, dusty chick down, etc.). See that there's good ventilation in your brooder.