It looks like the normal fade to me. Notice the faded flowers which have areas almost nearly light pink to white on the right side of your photo. Perhaps that end of the bed receives more reflected/radiated heat and the flowers fade faster due to that heat? Or, perhaps the light is stronger at that end of the bed. If the other flowers had no light pink to them at all, I'd think something potentially was amiss, but there are partially faded flowers on the others and that leads me to believe the cause is simply stronger at that end of the planting than at the right end.