Leigh, I'm so sorry about Sorenson's loss.
Oddly, I had a rooster die with similar symptoms. I had him necropsied by a veterinary pathologist -- my state will do it for free, and even though I'm a vet, why not take advantage of a pathologist nearby -- and there was no sign of heart disease, and in fact, she could not determine a cause of death.
I have his full brother here if none of his sons work out....I agree....these red and white ones are delightful.
ETA: Sorenson was an early March baby, came directly from GFF, about 3 weeks younger than Viking, which came in my first GFF shipment. I had four roosters colored exactly alike in that shipment. I kept one, you got one, and the coons took two (sigh...but their loss led to me getting the dogs).
Oh EEK!!!!! That is sure not what a SFH should look like!! Cute, but way too much, huh. I certainly can see why you let him go.
Well, on one hand, I won't have to worry about it....the one that had the most trouble hatching (vaulted) died on his own the other night. Another one, normal skull, passed too.
On the other hand, I have sold the rest and made it very clear they should be careful to avoid crested x crested crosses to reduce embryonic mortality as well as chick deaths and then issues later on...why create something so easily avoided?
ETA: and another thought....breeding crested x crested might be letting them do their thing, but...when you think SFH, what comes to mind? Is it a bird with no crest, a small crest or one with a huge crest? Nowhere in the writings of the breed description that I have seen does it say a large crest is acceptable. No, there isn't an official SOP, but I have seen various writings, and none say large crest. For example: http://www.swedishflowerchickens.com/breedinformation.html
Note "small coif" and addresses that those birds come from one specific area. That sort of makes me wonder if there are actually two sub-breeds of birds that look similar but are different in some respects.
You know when you get those occasional "whoops" double crests you should see if someone breeding frilkies or show girl types would like them. That double crest and and a naked neck could look so cute.