Sounds like to me it is a over feeding issue in conjunction with increased waste production by the remaining inhabitants.
The steps you have taken to clean your new/used filter should have been more than adequate to remove any residual bleach IMO.
Yeah I am leaning towards overfeeding + more fish waste + filter change
Sooooooo 30% water changes daily, anything else I should do? So far **knock on wood** the clowns don't even seem to care. They are acting normal, and continue to beg for food...