Marigolds, Vincas, Annual Plants.. Why>>>>????

I have a garden of flowers with vincas, marigolds, etc.. The vincas are doing excellent, they growed very fast, but all my marigolds are dying. And it takes long weeks for the to die. They look perfect in the beginning, then it starts to get like dry and then finally the look burned. I put them vitamins every two weeks. What is going on with my marigolds? I have sprayed bug killer just in case there isa bug eating them, but it still. Please help!!

Marigolds, Vincas, Annual Plants.. Why%26gt;%26gt;%26gt;%26gt;????
Okay, let's start with this info:



Marigolds require full sun and grow best in well-drained soil with plenty of organic matter. Prepare your flowerbeds by mixing in pine bark or leaf mold to 6 to 10 inches deep.



Marigolds can be purchased as transplants or seeded directly in the garden. Start seed for transplants inside four to six weeks before planting out. Most marigolds are hybrids. If you save seed from last year’s plants, they may not be the same as what you grew last year.



Plant each plant slightly deeper than it was in the pack. Plant French marigolds 6 to 9 inches apart and African marigolds up to 18 inches apart. Water thoroughly.



Keep a close check on water during the first 10 to 12 days. After that, water thoroughly once a week if it has not rained at least an inch that week.



Check out that water requirement! Very much! And is your soil okay?



Also, you may be overfertilizing. eHow.com says: Fertilize marigolds every four to six weeks, if desired. Organic gardeners may want to simply work in plenty of compost at planting time instead.



References and additional info below. Good luck - sorry for the loss.
Reply:Marigolds are a favorite breeding plant for red spider mites. To check if those demons are the problem take a piece of white paper. Hold it under the marigold plant and give it a gentle thump. If you get tiny specks (like pepper) on the paper, then spider mites are the culprit.
Reply:They need tons of water if it is hot where you are. That is the case here in South Carolina. My vincas are doing great but the Marigolds wilt every day. We are watering them twice a day. Try some other plants like day lilies. Check out my website at www.screaltorgreg.com