Meat birds sneezing and extreme shedding of their feathers

[farmgirllvo]

Hello everyone. I have been raising chickens for about 4 years now and meat birds for the same. Over the years I've learned a system to keep them growing and healthey. The only thing I've changed this year is the fact that I'm now soaking their feed and adding kelp gran to their feed. A few days ago i went out to feed them and realised they were sneezing and they clearly had lost feathers. I raised the light thinking they were to hot and had started pecking each other, but that didn't help, i raised it more and they just got cold. I would like to be as natural with this all as I can, so I'm wondering what to do.
I clean out their pen and give them fresh wood shavings twice a day.