Did you separate the two white supply conductors from each other so that
each one only serves the loads supplied by the black wire from the same
cable. *If not you will want to go back and do so. This will prevent
either one from being overloaded by the current from two breakers if the
white wire from one of the circuits goes open up stream at some later time..


Yes, I capped off the hot, neutral, and ground wires from the circuit
that was servicing the old lights. I re-checked all breakers and now
each one serves only one circuit. I'm confident that I fixed this
error on the part of the original electrician (or previous homeowner),
but it does make me wonder how many other mysterious and potentially
dangerous conditions exist within everyone's home.