Hi Chelle! I am no expert by any means.. but I have always had petunias.. in pots and in the ground.. I find that they need lots of water!! I water mine everyday.. especially the ones you have in pots.. as they can't retain moisture as well as those that are planted in the ground... I give them a good soaking... The ones in hanging baskets I water until they drain out the bottom.
One of the HUGE hanging baskets that I bought this year isn't looking so hot.. and I was tempted to take a picture of it and post it here.. but I am thinking I will give it a good drink of Miracle Grow and see if that helps.
Another thing that will help is to dead head your Petunias.. you didn't say whether or not you do that.. It will encourage new blooms.. and can be a full time job if you have alot of them.. or very large plants. I have gotten to the point where I don't pluck my big hanging basket.. I shake it!
Gently of course, but I give each clump of branches hanging down a good shake!! Load of old blooms fall off.. making way for new!
I am sure some of the more expert gardeners will come along to help you as well.. I just wanted to share my two cents.. Good luck!!