Ran short of water.
No way to change those leaves. Many folks remove them but I keep leaves without disease even though they have those dead areas.
When you think about, the green parts are contributing to the plant's health.

So more water will cure this?

The light colored spots are dead.
The green area is live and functioning.
Evenly moist soil is the goal when growing tomatoes. Don't allow them to get behind again.

Check the underside of the leaves for spider mites. They can cause stippling.

That's not stippling. Stippling from spider mites resembles pinpricks.