I'm not sure what you are asking. If you have already appointed all three as Poa, then the deed is done. Did you ask them beforehand if they were happy to do it? Have you changed your mind and want only one poa?
It can be stated on the forms that they can do it ‘jointly or severally’ - in other words, if e.g. 2 were away or otherwise not able to act, the 3rd could act or decide alone.
We have appointed 2 x dds to act ‘jointly or severally’.