The photos are out of focus.  We cannot say for sure what is going on with the chestnut and there may not be a single cause.  We do not have enough information. We notice poor color, there may be poor growing and site conditions, too much moisture, has there been construction in the root zone or nearby, we cannot see the canopy of the tree, is there branch dieback, etc.

Marian

Thank you for your response. I will try to take better pictures next time and send them to you or another expert. Do you know what is causing the dead ends on the Chestnut? That is my main concern. It is very unlikely that there was disturbance going on, since it is inside of a botaincal garden I have 3 Chestnut at home, and I have saw ends ends too.

You are welcome to send us more photos in focus.  Please give us more information. How old are the trees, how are they cared for, site conditions, etc.
Please send photos of the whole tree, around the base, and affected foliage/branch tips so we can see what you are dealing with.

Marian

Hello again! I have a picture of the entire tree. I hope this can help you with your conclusion!

Our plant pathologist does not see chestnut blight. Beyond that, we do not see a specific disease or pest.  
The fact that it has yellowing extremities, and is not irrigated while many places are experiencing drought, it may be that it is showing the result of drying roots.  May need water.  

Keep an eye on your trees. 
Water your trees deeply when you do not get at least 1" of rainfall a week from spring throughout fall. Many plants die from killing fall droughts, but don't show symptoms of distress until the following late spring. You can also check the soil and water when the top 1" of soil has dried. 

Ellen
  

Thank you for your help!

Our pleasure.