So many questions: Where are you, state and zone? is it a potted tree? If it is, how long it is in a pot. If not, how long it has been in ground? A seedling or grafted tree? Was it sprayed with anything lately?

There are so many variables that could contribute to the condition of your tree.

California, valley, potted tree about 6 weeks... When I planted it in the pot I had put an organic fertilizer for fruit trees. It was a grafted tree from Lowe's... Had not been sprayed with any pesticides. The leafs started to droop down about 2 weeks or so ago

What kind of potting soil did you use and how large is the container? Both of these issues can have a major impact on water retention.....or not. Once a week may be too often or not often enough depending on your answers.

Just an FYI but moisture meters are hugely unreliable........

Boy that sure looks like a lack of water to me. Is the water ruining out the bottom of the pot? Ca valley, there are many valleys in Ca.(born there) which one? It makes a temperature difference. Are we talking, San Jacintro, Murrita, Owens, or somewhere near Bakersfield etc.

Once a week in a pot isn't enough water. It's probably dried out and the water is just running thru. Set it in a saucer such that you can hold water about an inch deep around the bottom of the pot. That will allow the media to rewet by wicking up from the bottom.

If it is from being too dry it should look better in a couple days. After it gets going again don't drown it by standing in water all the time. Let it dry out some between waterings but not so much that it droops again.