Do you have any signs of botrytits on the foliage or nearby plants? This is the only thing I can think of causing brown petals at such a young age.

Here is a link that might be useful: botrytis on dahlia flower

Have you had really hot weather? The buds can get burned & look like this when it's really hot when the buds are forming. We had a bunch of them in July when it hit 103 for 2 days- fried the buds & then when they tried to open they were all deformed & twisted. Lopped off their heads & when the weather settled the new blooms were fine.

The foliage looks great but is has been hot lately. Not super hot but in the 90's once in awhile. I guess I will wait and see if the next flowers will be any better. Thanks for your replies.

That's interesting Plantlady. We hit 106 and 108 those hot days and though I've had some hard green centers I'd care to forget, I didn't have any brown buds at all. I hope it never, ever again reaches those temps here in Washington! Too much heat for me.