^^^^... Sorry to hear it.
My last losses were my pearlscale and punctatofasciatus butterfly on the same day.
Everything in the tank has always been quarantined/treated. A few days before, I had added a quarantined CUC, snails, hermits, a cucumber. They were quarantined like every other invert, 6 weeks in quarantine. With no substrate/liverock, heavy feeding, and heavy vacuuming it usually works just fine, but it got through this time(I'm thinking the cucumber had some ich cysts in it's gut still). Two days after introduction, my male Potter's Angel was dead. Water was great and other than some minor hermit scavenging, looked to be in good shape. Everyone else seemed fine. The next day, my pearscale, punctatofasciatus, and flagfin angel were breathing heavy. I decided it had to ich even though it wasn't visible, as it's the only thing that has the potential to make it through an invert safe quarantine. Due to the number of fish, hyposalinity in-tank was the only option. I removed all inverts(complete tank tear down required) and started lowering the salinity. Everyone started to perk up. The next day, the two butterflies were dead and the flagfin was covered in spots. I got the salinity down to 11.5 ppt throughout the day. Since then, everyone is doing great. My harlequin tuskfish hides constantly, but he's still fat so I'm trying not to worry. I'm not sure what I'm going to do about my invert quarantine to prevent this, I'm not sure they can last much longer than 6 weeks in such a sterile environment.
If you hadn't noticed, I hadn't vented yet...