It's because daylight hours are now shorter. Also with the breeds you have, I recommend not feeding layer feed, it's not formulated for heritage type breeds. I suggest switching to a 20% Flock Raiser type feed, or Chick Feed. Dumor 20% chick feed is cheap, excellent quality, & has a complete...
In my research I saw that Minorca was in their ancestry.
That's an old picture of Goober, he died of intestinal cancer a few years back at the age of 2.
What does your feed stores have? Getting that info will help us suggest a good brand.
Giving him a regular diet of feed will help his situation.
If he's doing that, I'd personally soup him.
It's molting season, everyone molts at their own rate.
May I suggest not using DE? It doesn't actually take care of lice/mites, & it's terrible for the lungs. If you want to kill mites/lice successfully use Permethrin Spray, or Dust.
I've gotten similar body types as well from specific crosses. Only Mediterranean within him comes from the Buff Orpington Lineage as Buff Minorcas were used in their making.
Some Mediterranean breeds have similar body structure as well, & tail type. I suspect leghorn somewhere in his lineage. Possibly Andalusian based on the leg color.