Good morning.
Thank you for your pictures and reports even if there are bad news.
I also think, the chick is dead and hope it was not the fungus.
Yesterday the 3 big siblings looked good. There was no sign of any illness.
I hope, all goes well for the 2 remaining chicks.
Edit:
Storkcenter writes they have found the dead body of the little stork under the nest, saw also the dead chick in the nest. They have so far no idea about the cause of death.