I noticed one evening that the lettuce on one side of the Tower Garden was wilting. The rockwool was very dry.
So I pulled the top off the tower and cleaned out the holes. (I turned off the pump first. Didn’t want to get an unwanted shower.)
The next morning the lettuce had revived. But that evening it wilted again. This time I manually ran the pump for awhile and the lettuce revived again. But when it wilted again in a few days, I took a good look at the timer on the pump and discovered that it would quick tripping the pump on each evening about the same time. Something in the mechanism had broken.
Today I went to Menard’s and purchased a replacement pump for $6. All seems fine now.