Banggai cardinalfish addition to the tank

My father-in-law's tank has issues keeping fish I think the issue is with the clown fish, he has a 70-gallon tank. I think the issue is with the two Clarkii clownfish are bullying the other fish.

I decided to get some Banggai cardinalfish and figured I should get at least 3 so that the could school and possible put the clownfish in check with safety in numbers. As soon as they are dropped in the tank the female came at them, all 3 of them turn and look at her and she comes to a stop, backed away and seemed to keep her distance. Figured the small school did it. (Picture shows only 2 of the 3 one of them seems to like to keep to himself half the time and then come back to the group when threatened.)

Later that day they are all gone... figured it was a bad sign. After searching for some time I found one in a hammer coral. I dropped some food in the tank and all 3 of them came out, I did notice that their first dorsal fin did not look quite as long and looked like it had been damaged on all 3 of them. This is just hours after being introduced to the tank.

Other fish in the tank are Bicolor Blenny and a Coral Beauty, while the Coral Beauty does not seem to pick on anyone he does not seem to be phased by the female Clarkii.