Add water or water and nutrients

I'm half way through my second single DWC 5 gallon bucket grow.
I change my bucket once a week. Later in the grow when the water level drops before bucket change day I usually add a gallon of nutrient solution.
When I change the bucket I test the ppm of the old solution. It's usually crazy high. 2000ppm to 2600ppm.
Should I be adding water only to get me to nute change day?

That's what I do. I catch and save the rain water from my roof. I mix their solutions and change water on sundays but if they get light I just add more rain water after ph-ing it of course.

Try adding back just water then test that when you change. You should keep the water level constant with a daily adjustment.. If i were running a bubble bucket, i would do the first weeks replacement of used volume, with water, then test to see if i could use a half strength feed back for another week or so..