3 x regulator 7805 for the same source
There is no inherent problem in using the same source for several regulators. 

One aspect might require attention- if the individual parts of your project communicate with each other via logic signals, say, then if there is, say during power up or power  down, more than a few hundred millivolts difference between the outputs then there could be issues. Using the same part types from the same supplier reduces the likelihood of that.