Q.Why is our tangerine tree dying?
Tons of leaves are falling off along with tons of blossoms. The tree’s beautiful dark green color is fading as well. I put down a cheap weed & feed about a month ago & it killed a lot of our grass. Could it also be killing the tree?
It is certainly possible that the weed and feed could have affected your tangerine, though not likely because the tree is so much larger than the grass. There are a couple of questions you might ask yourself -- was the tree all right until the chemical was applied? how long have you had it and how much has it been fruiting for you? Here is an article that might give you some food for thought: http://www.crec.ifas.ufl.edu/academics/classes/hos6546/materials/Smith.pdf
You might want to have the soil and leaves/branches/fruit analyzed by the Extension Service. (This link will help you locate a nearby one: https://www.gardeningknowhow.com/extension-search/
You might also take in some of the weedandfeed, if you have any left. If there's a product out there with something wrong with it, the state might want to know.