Sue, when I think about it, the problem is very much a problem of the elevated bed. It is 4X15 and 3 feet high so I don't have to bend over much. It is partially shaded at midday and can catch strong sea breezes. It is watered by sprinkler during dry periods.
I will see if I can get a 10X lens. I have regretted many times selling my dissecting microscope when I retired. I will examine the top of the roots when the next topple happens - which looks not far off.
So far, this has happened to six out of 81 large seedlings in the bed.
