Repotted Zygopetalum into 3 last yr, black spots on old leaves.what do I do now?

[YorkieF]

Hi All
I'm new to all of this but am being quite successful at reviving old phaleonopsis that have been neglected. Two years ago, my wife was given a Zygopetalum which re-flowered a year later.
With the new growth starting to make the pot tip over, I decided to separate the plant into 2 when the flowers had finished. It ended up in 3 pieces as one fell off without any roots. So I potted them up.

They all have new growth but there are black spots on the old growth. As you can see from the photos the new growth is on the opposite from the old as I had trouble keeping the old growth upright after potting.
Shall I chop off the old growth with the black spots or just wait and see.
Thanks
YorkieF

pS One of them has a flower spike starting in the new growth