I'm crazy about petunias. I have 5 hanging baskets and 6 containers on my deck. This year I decided to do 1 blueberry and lime jam container and one that is black pinstripe and white. Tell me what you think...yes, I spend alot of time deadheading!
I think they look terrific, you should see my pitiful ones. How do you keep them looking so good? I buy nice hanging baskets and after about a month they are ready to toss. I water them, give them some liquid fertilizer, but something I do makes them worse instead of better. They have good drainage, they are under a roof on my back deck, so they get lots of indirect sunlight and some direct sunlight.
Only remove the spent flowers. maybe your over feeding the plants as remember they are in a very small amount of soil when growing in a hanging basket, also any plants that are growing by hanging in baskets dry out pretty fast compared with plants of the same type growing either in a large tub on the ground or in the garden soil n borders.
If I were you, several times a week I would put the baskets into a basin or large bucket, allow the soil to take up as much water as it can, stick your fingers into the soil so you will know how wet the soil has become after a few hours (you need to finger test before you pop into bucket / basin so you will know. only give a liquid feed once a week and NOT too strong or you can do more harm than good if you over feed. I drop my baskets into a bucket at night and rehang it again in the morning, after doing this a few times the plants will burst into bloom with a smile.
I also think there are 2 types of Petunia growing in Gracesmum pictures, I think the coloured flowering type are hanging / weeping and the white are more upright so every lot will look different no mater where you grow them or how you do it, the most important thing is to give them the right care and best growing conditions to see them through a long hot summer.
Best regards. WeeNel.