Your plants should be fine. Usually problems arise from the roots or the crown (center of the plant). I'm not sure what the hollowing of the spike could be...maybe post a picture of it...Unfortunately when you bring plants home from the store they have already been in bloom for a while and they don't usually get the best of care while at the retail stores while there (at least the ones around me ) so the flowers usually drop off soon after getting them home. If you are worried about the surface roots drying out spray them with a spray bottle slightly every day or every other day and water fully when you notice the roots deeper in the pot getting dry. Based on the picture it looks healthy to me.