Hey Shamous,
Whenever you check back for answers to your question please know that many of us can sympathize with your problem. We can grow the difficult to grow
plants but can't grow the easy
plants. However, there are some possibilities you may have overlooked with your petunias. First, many of our fabulous forum pals religiously discuss and promote that "the secret is in the soil." It is. Be double certain that you haven't planted this
plant in previously used potting soil. Sometimes we do this when we don't want to go buy new potting soil and we inherit a previous
plants problems, bugs, viruses, etc. You may need to replant in better quality soil. As stated above, discount soil isn't saving you anything and costs us in problems later. Next, sometimes my wife and I accidently duplicate the others efforts. I water, and she waters later. I fertilize, she fertilizes later. Spray for pests, she sprays later. You get the idea. Usually our problem is too much water. The other problem is the soil looks wet on top but isn't soaked through to the bottom. Sometimes drainage is so good it goes right on past the roots and out the bottom without the
plant absorbing anything much. The next thing is too much fertilizer, I like the Miracle Grow products but have learned to prefer the organic methods of compost tea, horticultural molasses and earthworm castings. I get much better results and improve everything as it goes, or grows. So, soil, water, fertilizer. Bugs and other pests probably aren't it but maybe, check closely and use glasses if you need to but don't like to admit it like I do. You may have gnats in the soil. Perhaps slugs are crawling up into the basket at night time and crawl out before dawn. Be sure to pull off the dead leaves as soon as they are done looking pretty so they don't set
seed and will continue to produce blooms. Other than that, we sometimes have to accept the fact that there are some
plants that are healthier than others and you may have bought a dud. Genetics are a factor. Where did the
seed come from? Could be from the
seed of a hybrid that leaves new
seeds of crappy quality. Surely and hopefully this will help you to discover the real problem(s) and solve them. Sometimes it's just easier to compost the darn thing and buy another one. But then we wouldn't learn anything would we? Good luck!
Terry in Texas