How can I measure the current and voltage of each source in a DC circuit with multiple sources?
Yes you can do this. If your DC bus voltage remains constant then this is just a matter of measuring your DC current in each branch and multiplying by the voltage if you want to calculate power.



Figure 1. A 5-channel AC/DC current sensor board.

A quick web search for DC current sensors throws up many results such as that of Figure 1. Generally these devices use Hall effect sensors embedded in a slot of a torroidal core. The Hall sensor measures the magnetic flux in the core and responds to DC as well as AC (whereas a regular current transformer is AC only).

Linear make a range of high-side current monitoring devices if you wish to roll your own. 



Figure 2. Linear LTC4151. 0.02 Ω is probably for a high current.

This particular one seems to use serial transmission. Analog versions are available too.