Q.Looks Like My Plants Are Dying

We recently moved and I was able to start fresh with a clean slated flower bed. Our new house faces the west where the old house faced the east. When I transplanted my perennials, they did real well at first and now the leaves are turning brown and they look like they are dying. I have three astilbe plants that aren’t doing too well and look like they are dying. I have fertilized, made sure there are no pests. I thought that maybe I wasn’t watering enough and then was afraid I was watering too much and was killing them that way. I read that they like shady areas and was wondering if they might be getting too much sun. The same with my hostas, the ones that are on the end of the flower bed are doing much better than the one that is in the sun the most. I was thinking about moving them around.