Sunday Sunlight and Dogwood Worries

I took this at the end of April of this year.  Our dogwoods up here are the species Cornus Nuttalli, the only dogwood native to California, also referred to as the Pacific Giant as they can grow up to 60 feet tall, and their range is from the Southern California mountains up to British Columbia.  This blossom is strange in that it only has 4 petals - well, they're really called 'bracts.'  The center of the bracts contains the little ball of the actual teeny, tiny yellow flowers and the showy bracts just serve to attract pollinators.  Cool, huh?

Anyway, usually they have 6 bracts.  But some of the trees only put out 4 this spring.  I'm wondering if it was because we've had such a dry winter.  Dogwoods are terribly suceptible to the disease Dogwood Anthracnose, which is a fungal disease that kills them, but all the gardening sites I've researched haven't said that putting out only four bracts is a sign that the tree is infected.  So, I guess I'll just keep my fingers crossed and give them plenty of water.