Q.My Oleander Is Dying And I Don\’t Know Why.
My oleander had spider mites over the summer, i sprayed it as directed with a safe miticide, until mites were gone. Before bringing it in the house for the winter a friend of mine suggested I shower it to remove dust and so on. So I did and after the shower the leaves were left with a white color. I looked online and it said it could be calcium from the water and would fade off eventually, It did but leaves started getting crunchy, I thought I was left over remnants from the damage the spider mites had caused but that the new growth would be fine. I also kept spraying it once a week with miticide for about another month just in case. Now it’s been a month since I stopped spraying it and the new growth seems to be curling and growing crunchy as well and some branches seem to be turning black. At this point I have no idea what is wrong or if it can even be saved… Any help is appreciated…

Certified GKH Gardening Expert
Unfortunately, your photos did not come through. I am unable to see the damage. I can assume that the spider mites have done it in, though.
They carry diseases and will, almost, always infect the plants that they are infesting. You can try a number of fungicides. Copper fungicides will be your best bet, since you will not be consuming this plant. Here are some articles that will help:
https://www.gardeningknowhow.com/garden-how-to/info/what-is-copper-fungicide.htm
https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm
https://www.gardeningknowhow.com/plant-problems/pests/insects/spider-mite-control.htm
https://www.gardeningknowhow.com/plant-problems/pests/insects/spider-mite-treatment.htm
Here is a collection of articles that will help you to care for Oleander:

Check out this article for some possibilities: https://www.gardeningknowhow.com/ornamental/shrubs/oleander/oleander-leaf-curl.htm