Lordy I remember being the strange orchid guy in college. Because window space was nonexistent I actually converted a decent sized aquarium into a terrarium and grew a number of compact plants. Good times.

How often are you watering? And can you get a better picture of the damage in question? I don't see the tips you're concerned with in the photo you provided.

I water about once every week or week and a half. The tap water here is pretty salty, so I make a special trip to get filtered water from another building on campus. Here are a couple better pictures of the plant:

Here's a close up of one of the leaves that has spots on it.

Lets try a second time, got booted the first attempt at replying:

I suspect watering is your issue, too dry. You have a small, relatively moisture loving oncidium in coarse bark, in a pot with a ridiculous amount of holes (yes, its an orchid pot, I'm aware).

I'd prefer to see this small plant in finer medium. Fine fir bark, or with sphagnum moss added to this mix (for me, preferably the former). And I'd prefer to see it in a solid pot, clay/ceramic/plastic. A dorm room is too dry for a moisture lover in an orchid pot, in my experience (of course, YMMV).

I REALLY want to say something about the water, but I need some more info.
1) How is it filtered? Reverse osmosis?
2) Is it softened?
3) Is this the only thing you use when watering? Do you amend it in any way?

This post was edited by terpguy on Sat, Nov 23, 13 at 14:55

This won't make you happy. I live in Brazil and can't grow Oncidium Twinkle. Whoever first hybridized it should be condemned to an ice desert. It just dies for no reason I or anyone else can figure out.

Not true. Just top water as you would any other plant.

So the water doesn't sound horrible. But all we know is that it's filtered and have no idea what the TDS is. That burn is reminiscent of salt damage, which is exasperated in dry conditions. I'd be happier if you used distilled water with either some tap water mixed in or supplemented with weak fert dilution at each watering. But one thing at a time. Let's address potential dryness first and see what happens.

This post was edited by terpguy on Sat, Nov 23, 13 at 20:38

I think the word you wanted was "exacerbated", Terpguy, but I like your word better! As I said in another post recently, my oncidiums all seem to develop spot issues. They continue to bloom so I try not to get all bent out of shape over it. I spray with Physan 20 once a week and run a fan, but sooner or later, all get various fungal problems. Of course you're right about the moisture-loving nature of oncidiums, as I've learned. Which is probably why fungal problems crop up!

I actually was trying to type exacerbated. Damn autocorrect! :-)

I have a twinkle at home that displayed many of the symptoms as yours, and the answer was more water. A LOT more water. I completely immerse the plant every 5-7 days in a container of water with a half-dose of general orchid fertilizer, and let it sit there for 10 minutes. Thankfully, my tap water is excellent stuff, I don't need to filter. I also spray the base of the pseudobulbs every morning. My apartment is very, very dry right now. It's also in a small plastic cup with holes... it always has a little bit of water at the bottom.

Not only has it recovered (even the really, really shriveled one has plumped up), it put out a spike and has three new pseudobulbs popping out. The first flower opened last night... I hope all the rest follow suit soon!

Good luck!