The generic R7 Astromech card says you can only use it once per round. So if I have multiple R7 Astromechs, can all of my ships with R7 use its ability during the combat phase or just one per combat phase?

The cards have no effect on each other, so each ship can use its R7 once. Just as, for example, a quartet of Royal Guard Pilots could each use their own copy of Push the Limit once per round.

The generic R7 Astromech card says you can only use it once per round. So if I have multiple R7 Astromechs, can all of my ships with R7 use its ability during the combat phase or just one per combat phase?

If, on a theoretical ship that had multiple astromech slots, you had multiple R7 astromechs, then you could use it against multiple attacks.

Still, on that theoretical ship with multiple astromech slots, this would not be as powerful as getting an R2 and R2-D2 with Daredevil for 2 sheilds per turn, or R5P9 and R2-D2 for the same...

Per the rulebook, when an upgrade card says "you" it is specifically referring to the ship the upgrade is equipped to, not the player. So if an upgrade says "you may do this once per round", that means "the ship this card is equipped to may do this once per round".

The generic R7 Astromech card says you can only use it once per round. So if I have multiple R7 Astromechs, can all of my ships with R7 use its ability during the combat phase or just one per combat phase?

If, on a theoretical ship that had multiple astromech slots, you had multiple R7 astromechs, then you could use it against multiple attacks.

Still, on that theoretical ship with multiple astromech slots, this would not be as powerful as getting an R2 and R2-D2 with Daredevil for 2 sheilds per turn, or R5P9 and R2-D2 for the same...

Oh the possibilities, can I?

The generic R7 Astromech card says you can only use it once per round. So if I have multiple R7 Astromechs, can all of my ships with R7 use its ability during the combat phase or just one per combat phase?

If, on a theoretical ship that had multiple astromech slots, you had multiple R7 astromechs, then you could use it against multiple attacks.

Still, on that theoretical ship with multiple astromech slots, this would not be as powerful as getting an R2 and R2-D2 with Daredevil for 2 sheilds per turn, or R5P9 and R2-D2 for the same...

Oh the possibilities, can I?

Probably a good reason why we won't see that ship, but go nuts. Add a crew slot as well!