Spreading black spots oncidium leaves

[Sahlabiya]

Hi again,

I'm writing again about my poor Oncidium

I've been very careful to make sure it is not in direct sunlight and it has not gotten any more tannish spots so maybe those were indeed burn.

The black spots, however, are increasing, and when I look at websites that talk about the black spots that are fungus diseases, I think mine resemble the problem photos. The first photo is with the black spot leaf still on the plant

I cut some off tonight because I feel nervous about how they are spreading. There are other black spots on the plant but I cut the leaves in which the black has slightly eaten into the leaf tissue and left a dryish blackish (sometimes slightly rust coloured) indent. Those are the cut leaf photos. I cut six leaves tonight. I think all but one of them were directly attached to a pseudobulb. Some of the pseudobulbs are beginning to get black spots.

Also the new growth still seems to come in brown, as you can see from the last photo. I'm a little worried about the shriveled pseudobulbs too. I water once a week since I am worried about overwatering. I wonder if I should soak it longer when I do water?

[NYCorchidman]

I don't see any burn. They are all mostly likely fungal attack, which is common on certain oncidiums.
I do not like the look and usually stay away with any plants with spotted leaves.

As long as you do not mist the leaves (and even if you don't, those spots will still appear I find) watering do not have anything to do with leaf spot diseases.
If you water only once a week in this weather, you definitely want to soak for good half an hour or so.

[WhiteRabbit]

Onc can be prone to spotting, tho yours does seem very heavy. What are temps and humidity like? Any air circulation? I mostly only see heavy spotting on mine that are forced to winter outside in very cool damp weather...

Are pbulbs slightly wrinkled, or quite shriveled? Try using a skewer in the media to help determine when to water. You might also want to check the roots.