Please tell me what should i do whit my plants, and what make them become like that. Please help me because one of my petunia plant already died because of the same issue as this. Thankyou very much.
They likely are being over or under watered. Let the soil dry out between waterings. Here is more:
https://www.gardeningknowhow.com/ornamental/flowers/petunia/petunia-container-care.htm
How often to fertilize petunias is helpful
You should avoid spraying petunia leaves and flowers, completely, actually. This will cause disease, and they are susceptible to several. Carefully feeding by watering it into the soil is best.
This article will help you to grow petunias to their potential:
https://www.gardeningknowhow.com/ornamental/flowers/petunia/petunia-care.htm
This collection of articles will offer more information:
I have noticed a sparkly silver substance showing up on my petunias and marigolds. The marigolds are staying small and stunted, while it seems to be slowly killing the petunias. I have never seen anything like it before! What could it be?
Powdery mildew perhaps? You can remove the affected foliage and make sure the plants have good air flow and it is not so soggy and humid that it promotes fungal infections. I normally use a 40% milk + 60% water spray every week, soaking the everything well. Discard unused solution. Any kind of milk is fine.
Hanging bag of petunias. I would normally water every day that the bag felt light. But its been pretty humid. So, I assume that the water was coming out of the holes in the bag and running on the plant without drying. Why else would the underside of a petunia and leaves go saggy and brown?
Yes, this does appear to be an overwatering issue. They are very sensitive to disease from overly moist soils. A fungicide may help. Here are some article that will help:
https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm
https://www.gardeningknowhow.com/ornamental/flowers/petunia/petunia-care.htm
At what temp should I bring in outdoor plants? I have Petunias and Geraniums.
It depends on the type of each, but now would be a good time if you have not done so, yet.
https://www.gardeningknowhow.com/ornamental/flowers/petunia
https://www.gardeningknowhow.com/ornamental/flowers/geranium
I bought a. Large petunia plant and it is sitting in a decorative brown hay like bowl. Do I transplant that with the petunia?
I would not. I would transplant into fresh soil and discard the hay.
This article will help you with the care of Petunias:
https://www.gardeningknowhow.com/ornamental/flowers/petunia/petunia-care.htm
The flower petals appear to have been eaten by something. I cannot see a pest. Looking to know what it might be and how to kill it.
It could be a number of pests, from slugs, to ants, to aphids, or other insects. It could even be from fungal or bacterial infection. Unfortunately, your photos did not come through. I am unable to see the damage. You may try looking on the undersides of leaves for signs of infection or infestation.
https://www.gardeningknowhow.com/ornamental/flowers/petunia/problems-with-petunias.htm