The simple answer: Yes, if anything, flowering plants need extra feed. Your plants will need to be fertilized with a product appropriate to the media in which they are grown. In general, plants in a bark-based mix will need a fertilizer high in nitrogen ( usually in a 3 - 1 - 1 ratio), while a balanced food will do for all others (usually a 1 - 1 - 1 ratio.) If in doubt, feed with the same balanced fertilizer you use for your other container plants. Orchids will do far better with too little fertilizer than with too much. The old adage, "feed weakly, weekly" is very appropriate. Feed every week with a dilute solution. It is far easier to remember than "Did I feed last week, or not?"