Q.Fruitless mulberry tree death
I just lost a full-grown beautiful fruitless mulberry from possible root rot. What do I need to do to prevent my other full-grown tree from dying, too? It’s top leaves didn’t leaf out this year but the rest seems OK. It was hit by lightening twice last year. Was our drought to blame? Are gophers to blame? I’m always putting down poison for them. Should I water more, water less? I do feed 15-15-15 3x a year for the rose garden nearby. Feed the tree, too, or not? I am very worried about the tree.
It’s midnight here and I don’t have a photo to send, sorry.

Your growing zone is 9a.
The recommend growing zone for a Fruitless Mulberry is zones 3-9.
You fall into the range of this tree, but with the issues you have had, it would seem it's marginal to your garden.
Refresh yourself on the care requirements with the link below.
https://www.gardeningknowhow.com/ornamental/trees/fruitless-mulberry/fruitless-mulberry-trees.htm
I would also recommend you contact your local County Extension Office to enquire on the success of a Fruitless Mulberry Tree growth in your area.
Here is a link to help you locate the nearest office.