Ok you have some other problem that is causing the fish to die, it is not your acclimation. How are you testing? Something is not right here. Damsels should live no problem even without acclimation.
Forget about the acclimation, something else is wrong. Do you have a lid? Surface agitation? What test kit? How did you cycle the tank?
29g Mixed Reef, 150w 14k Phoenix MH w/ Moonlights, Reef Octopus BH1000 HOB Skimmer, Ecotech Vortech MP10es, ReefKeeper Lite (Plus), PH Probe, Temp Probe, ATO, Carbon/GFO Reactor.