OP, I agree your acclimation procedure is sound.
I do the same. On shipped fish, I use a 25g needle and syringe to puncture the bag for a sample and tape over it, float bags in qt, adjust salinity and plop the fish in quarantine.
So was the symptoms the same on all the fish, red spot on mouth leading to tissue sloughing off? Seems like I've seen a couple clownfish posted that have had the same issue..
@melypr1985 I think you may have responded to a couple recently?
It would be interesting to identify if this is indeed what you suspect, what I read seems to talk about food fish aquaculture... Would hate another bug to start becoming a more common issue...
Any other symptoms? Eating? Hiding, etc? Did you sterilize quarantine between each fish?
Sorry about your losses, hope you it goes better next time.