Don't dig them up. You don't need to amend soil for trees.

Can you post a picture?

How much water are they getting and how are you watering?

It's probably the heat. Cherries don't do well in the heat. It should start to get better by the end of September if you keep the tree consistently watered.

If you really wanted to go out of your way to tend to the tree, you could mist the leaves during the middle of the day (sometime between 12:00 to 4:00 ). I've even heard some people have very lightly sprayed their trees with mineral oil, or lightly rubbed some petroleum jelly onto the leaves, to help keep them from drying out.

It's the height of summer right now, and a little browning is to be expected. San Jose has clearer skies than San Francisco, so less protection from the sun. In short, what you are seeing is perfectly normal for the climate you are in. There's a reason most commercial cherry orchards are based in Michigan and Eastern Washington. Also, in San Jose (all the paved surfaces in the surrounding area has an effect on temperature) it's quite likely your kwanzan trees are not getting quite the degree of winter chill that they would prefer. This results in slightly reduced vigor, and that is also associated with browning of the leaf tips.

Your tree should fair better in future years when the roots have become more established (and they can provide a more adequate water supply to the leaves).

You get enough chill hours for this tree?

Also, cut those green shipping ties off of the tree beside the one you are showing.

Thank you for the info guys! My 3-1 Cherry tree is getting worse and worse. The top leaves are gone and I see clear/light brown sap coming out from the balding top branches. I amended the soil for that tree last week with Miracle Grow vegetable all purpose gardening soil and peat moss. I also got some black sun mesh.

About the chilling hours, I asked the local nursery that sold the tree to me and told me I should be ok? I know this tree is best for zone 5-8 but according to online info I am in zone 9. But I do see these type of tree around my area. So I am hoping for the best.

I will upload more pics later when I am home tonight.

I've heard some people use 50% shade cloth. In summer it helps cut down on the sun so the plant does not dry out as much, and in winter it can be used to shade the plant to keep it less warm during the daytime so the tree can accumulate more effective chill. (maybe shade from late May to early August, and then again from mid-December to early February)

You would need to construct a wooden frame for it though; you don't want the black-colored cloth resting right up against the tree, that can actually raise the temperature. (black absorbs light and turns it into heat)

This is not a requisite of course, only if you wanted to do anything and everything that was possible to help your cherry survive in that climate. It's even more difficult for those of us farther south.

I know there's some other flowering cherry varieties that do better with less chill hours, but the flowers are not quite as pretty, in my opinion.