Help identifying stem rot on struggling phalaenopsis

[AnnekeR]

Hi everyone!

I’m new on here and sadly, despite my best intentions I have a pretty poor track record when it comes to orchid care. I currently have 3 orchids, 2 of which are not doing so well, but I am determined to revive them if at all possible and would greatly appreciate any advice!

This little Phal is a couple of years old, and I finally got around to repotting it for the first time. Most of the lower leaves were yellowed and shrivelled and fell off when I touched the plant. Where they came off there was a black-ish and very dry section left behind at the base so I peeled back several dead layers to reveal the stem underneath. It seems pretty narrow and dry, but looks like maybe some new roots emerging? It’s not squishy and as far as I can tell it doesn’t smell so I was unsure if the leaves falling were a result of rot or just neglect?

I’ve also noticed a single small black spot
in the centre of one of the remaining leaves. Could this be an infection or perhaps sunburn. It was in a very bright window.

Thanks in advance for sharing your expertise. Really hoping this one still has some life left in it!