Ask-a-Dave's-Gardener: Hanging baskets punk out in a few weeks , 1 by Ksbradley21

Ksbradley21 wrote:
Hi all. I have a dilemma with petunia hanging baskets I bought at a nursery. Every year I try different types of plants but they all seem to get spindly and ugly within a week or so of bringing home. See picture attached for this year's pick. I water diligently almost every day, and I rotate for sun exposure, and I put small amounts of fertilizer every couple of weeks. What more could I do to keep them nice looking all summer? I explained to the guy at the nursery that they get direct sun almost all day, and they assure me this is ok for petunias or what ever plants I get.
I would really appreciate help with this one. I want my deck to be pretty and colorful all spring summer and fall. I live in north east in 6zone at the base of the blue mountains in Hamburg pa.
Thank you! For help!