Cascade 1000, live plants, pH was ~7.6, normal for my tank. Nothing new added. 2 large angels, 1 platy, and 1 tetra (and another tetra today) were found dead. Currently housing 3 platys, 1 betta, 2 black skirted tetras, 3 rosy tetras.
I think you're right with the new water, as no buckets are...