You have left out the most important piece of information and that is where you are in the USA.

Here are the American Orchid Society Cultivation notes for Oncidiums.

AOS Culture sheets

Those pin prick little black spots are often seen on the leaves of Oncidium Sharry Baby plants and are regarded by most growers as harmless.

Generally orchids are best potted in a pot that may appear too small to new growers and though best kept just moist they do not like to be continually wet. Remember, you are trying to copy where the plants ancestors grew/grow on a rock or on a tree.

I am actually in New Zealand which probably makes this all that much harder. Thank you so much for your link and help.

unless you're going to teach that sharry baby to swim, it is in the very wrong size pot. It needs to be in a 3 or 4 inch pot, with firmly placed media around its roots (no wiggle of any part of the plant allowed). Then sparsely water it until you see new roots grow. Indoors... keep it by a bright window///

North or South Island?

Despite all the warnings I've heard, I've learned oncidiums really like water. I would 1) put it in a smaller pot, and 2) use a smaller bark mix (seedling mix if you can find it in NZ. Their fine roots will be much, much happier. If you cant do that, I'd put an inch of sphagnum on top to help keep some of the humidity in the bark for longer. I heavily mist all of my oncidiums every day, and give them a good long soak once or twice a week. They can't seem to get enough of it, along with really bright light.

I totally agree with dannie's advice: smaller pot, smaller mix and MORE water. I soak mine weekly and mist daily and have rescued 2 from certain death which are now back to health and spiking.

Amazing differences. I never watered my Oncidiums until they were almost dry. Even in NY during the winter. Never, ever kept them wet.

In Florida, they go dry, dry. They bloom their heads off.

I do agree with smaller pots, no spritzing and smaller bark mixed with some sphagnum moss.

Jane

Thank you all so much for your comments. I'm from Wellington.

I'll definitely get a smaller pot and some smaller bark mix and spagnum moss. Will also give more water a go. We originally had both plants in the big pot and they were fairly happy so perhaps that is the problem.

My husband and I spent some time in Wellington on our honeymoon :) Gorgeous city! I'd love to live there one day.

Good luck with your Onc - just to clarify, I don't keep mine wet, but I do mist the top everyday to keep the aerial roots from drying out.

I agree with dannie too. Upper roots are too exposed. Smaller pot will be ok. However, if this plant is indoor all the time, there is no danger. Side leaves tend to dry off, this is not a big deal, just remove them. When upper leaves are yellow or brown on new growth so then plant may have a problem.

Thank you for your input, we are going to find some better bark mix and will cover the top roots. They are indoors all the time.