New fish not lasting

Im posting this on behalf of a friend.

Tank: 75g
No lighting atm
No sand atm
About 50 pounds rock
42x flow between 3 powerheads,* one aimed at surface for adequate gas exchange
79 degrees
Around 15 nitrate
7kh
Salinity 1.024
10g water changes,* 5g 2x a week to suck out detritus &* blow off rocks

Acclimation: float bag (if copper is in original water bag is not floated and this is done in a bucket,* ambient room temp 76),* add 1/4th cup water every 15-20min until bag full,* dump half repeat until bag full,* release fish

Fish added:
Banghai cardinal (copper)
2 weeks later
2x clownfish (copper)
2 weeks later
Kole tang (copper)
2 weeks later
Male anthias (not copper,* dies from relentless attack from kole tang in 3 days,* corpse promptly removed)
1 week after anthaia was added (3 weeks since kole tang)
Kole tang removed,* 2 firefish and 1 flasher wrasse (non-copper)* added
1 firefish and wrasse die within 2 days,* corpse promptly removed,* other fireish died after 1 week (exactly)* of being added,* wrasse and the longer living firefish were eating
2 weeks later (this friday)
1 carpenters wrasse added,* yesterday was eating but hiding,* today found laying on side breathing heavily,* just got a message saying its dead and not sleeping.

Both clowns are eating and healthy,* cardinal is eating and healthy,* i watched them swim around for a good hour before we went out and bought the carpenter wrasse on friday.* The tang was eating and healthy but very aggressive thats why we traded him in.* New fish seem to die but established fish appear completely fine,* clowns and card are not aggressive to new fish

Any clue whats goin on?