you may have fungus.

Had the same thing happen with my store bought ones. We got an inch and a half of rain Saturday, and I didn't look at them Sunday. Today they looked yellowish and shriveled. I just can't grow these wretched little things.

Please see photos to see if this will help diagnose my problem.
The nice picture was taken Arpil 18. The sick one was taken today. :

I know a few people in the Dallas area that have luck with Wave Petunias in hanging baskets but I am not one of them. I use a few Petunias early Spring just because I love them and as soon as the hot weather hits, they are gone. They like cooler summers. They thrive in places like MN and bloom all summer. I worked at a garden center here and hated to see people buy large volumes of them probably intending to fill a bed. If they asked me, I told them not to buy them. Lots of other plants that thrive in our area - why waste time and money with those (in volume that don't?

Since petunias are ONE of my favorite flowers, I try to always have them around. I have several hanging baskets and containers of petunias as well as a few window boxes. I just have to keep the roots moist and they do well for me. I do, sometimes, lose a few to heaven knows what, but I love them enough to kkep trying. I am sorry you lost all that beauty.

I have the same problem with zinnias ans perriwinkels.

Zinnias I can plant by the curb but only from seed.

sorry....fuzzy leaf plants have a hard time when there is a fungus in the soil. You can't know until this happens.

Hanging baskets are one way of having them

sighhh
c

Here is a link that might be useful: fungal problems with petunias