As Christie said, sun or heat could be an issue. 2011-2014, I had one dedicated Amaryllis bed in full day sun. Each season, they produced less and less blooms and the foliage died back too soon, so the bulbs didn't have the energy to produce the next year's buds down at the basal plate. In order to save the bulbs, I moved them into a bed that gets sun after 2PM in the afternoon. 2015, they didn't bloom, as the bulbs recovered, but in 2016 they bloomed heavily. With less sun, the foliage looks better and new leaves appear through the growing season. Some people plant them under a high dabbled shade, again so the bulbs get about 1/2 day of good sunlight. Having them in a planter does allow you to move them to a better location. If you water once a week, give them enough so the water drains out of the drain holes in the planter, then let the soil dry out again. I would advocate not sticking to a "time" schedule, but watering when the soil feels dry in the root zone. During the hottest part of the year, that could be more frequently than once a week. Just avoid water on the neck, if you can, wet the soil. There will be a recovery time, perhaps a year or two, but if too much sun was one of the problems, you should eventually see a big improvement.
