Sorry to hear about the loss.
Have you tried raising the temp to 84 deg to lessen the life cycle of the ICH? If not, you may want to induce that immediatley to try and save the PT. Are you treating with chemicals to rid the ICH? if so, which one? Lots of questions, however just want to know more bout the issue.
Judging by the sound of the problem with the angel, it must have had something also, prior to being introduced into your tank. Maybe at the LFS