Strange Dahlias

I have had some beautiful blooms from the Dahlia tubers that my father gave me from his allotment. However these ones have been acting a little strange, the first six or so blooms were stripy like these, then it threw out one completely red bloom with no stripes ( sorry didn't take a picture)



If that wasn't a bit unusual, the plant then surpassed itself itself by developing this bloom ....

I have never seen anything like this in my life, I can assure you there is no camera trickery involved the flower has developed like this - I can barely blog - nevermind meddle with photos !!

Does anybody know anything about Dahlias or have any idea why this would have happened - my freaky flower currently has pride of place on my kitchen windowsil !