Don't beat yourself up over it Mrs. Nicky this kind of stuff happens.
I've got 6 Aussie rainbows in with my gar it started out with 8 of them lost #7 tonight.
I also have a lot of WC minnows, rosie reds, guppies, and 4 GF in with him.
BUT!
I new full well what could/is happening to the rainbows since there is no way out of the tank.
They are 3 inches the gar is 9 inches.
When I bought the gar there was a 10 inch CK & a 4 inch oscar in with him. the 4 inch oscar was picking on the gar & gold clown knife, BOTH fish that were 2x plus his size.
Just another example of how aggressive a cichlid can be.
One more thing that goes back to size with cichlids it doesn't really matter, temperment and territory matter more.
They are very unforgiving when it comes to sharing a domain.
Rich