thoroughbreds and kois

It is a very sad day today. At least 16 of my adult and big koi fishes are dead... I dont know what happened. they had these reddish marks on their bellies and their eyes were becoming white.... I dont know what to do except to bury them at the nearby lot.. I tried saving them by using a lot of medicines but to no avail.... Maybe they are not really meant to stay.... Anyway, thank you to all of them...they brought immeasurable joys to me and my family...