Phal problem - bases of leaves turn yellow, stem black

[AnnieM]

Hi,

I'm so glad I found this forum. I have a Phalaenopsis and it seems to be sick

I bought it in November, in full bloom, flowers have withered in mid-January, I believe it was just the end of its flowering season. I cut the stems back when they dried (except one that still had a withering flower on it two days ago). The plant is not kept in direct sunlight, fertilized once a week as I was told, potting medium is bark. I water it once a week and sometimes I sprinkle water on it & keep it on a humidity tray, as my apartment has extremely dry air.

Yesterday I noticed that the base of the leaves turned yellow, the leaves (except two) fell off when I touched the plant, and the stem is black or very dark brown. These problems appeared very fast, last week the plant was healthy. The roots look healthy, nothing is musty, there's no bad odor and no sign of rotting. I looked around in this forum and I'm unsure if it's a rot (I was unaware that water shouldn't get into the crown when I was watering, but it's not likely that much water went into it as I usually poured water on the potting medium) or maybe it is some kind of fungus. I'm a bit scared to use hydrogen peroxide, expecially that I don't know what the problem is.

I try to attach a picture (in case the photo is of bad quality, that black rod on the left is not a stem, it's the thing supporting the stem.) Any advice would be appreciated, thanks in advance!

Annie