Muster support skill gem doesnt work (minion support gem)

its supposed to increase the dmg of minion by 7% for EACH diferent active minion

it only aplies the 7 % dmg increase once . it doesnt care how many other minions are active . its just 7% dmg increase

if i have ALL other minions inactive except the one its on . still just one time upgrade , if ALL active , still just one dmg upgrade

im using diferent kinds of specter gem and ratling scepter to have diferent kinds of minions , it doesnt even increase the dmg when i have the skeletons from the scepter active