Thank you very much, Barbara and Christie. Your information is very helpful. Although I do not like using chemicals, I might make an exception with my Hippeastrums.
This has not been a good spring season with them, because of additional problems in Paradise: last year, rabbits ate the leaves (and a small portion of the bulb) of a large planter full of white w/red stripes Hippeastrums. This year they did not look good and had poor leaf growth and no flowers, so the day before yesterday I dug them all out, to replant them in a fresh mix, only to find out the bulbs had reduced their size to the half. I have additional problems during summer with very poor water supply, but they got water at least once a week. As I recall, the ones in my parent's garden did not get much more than that, but grew large bulbs and gorgeous flowers.
I really hope I can recover my babies!