Oncidium Twinkle new leaves yellowing
 

I've had on Onc. Twinkle for several years, the first 2 years after purchase it did great, bloomed each spring and grew well. Last year I repotted it and I did not keep up on watering and I let it get very dehydrated, the pb all shriveled up and I did not get any blooms this year. So I repotted it again, cut out the dessicated roots, and started to water better. The good news is that the pb have all plumped back up, I have several new growths and new roots forming. The bad news is now I am getting newer leaves yellowing (not the old leaves just new smallest ones).
It is potted in a small/medium fir bark mix labelled for oncidium type orchids (from local orchid nursery). I have it under LED lights where it did fine in the past. I get occasional burns on the leaves if not careful. The current temp in my house is 68 - 70 daytime and 65 nighttime with humidity in the mid 40s usually. I do have humidity trays.
I have been using rain water with Green Jungle Orchid Fertilizer each watering with a water only about once a month. I have not been letting it dry out since that was the issue before, watering about once every 5-7 days. Maybe too much water? I thought it was a light issue but searching the forum it seems like a watering issue. Should I let it dry out more?

Are you getting wrinkled leaves, too, or just yellowing?

Your humidity is about as low as mine ever gets in my grow room. My Oncidium hybrids get bright indirect natural light, and have never had burns from the light. One that came in bloom last October is in spike again now. I don't have yellowing leaves, but I do get accordioning / rippling of new growths on all my Oncidium hybrids if I don't water enough. I actually have to stand my plants in dishes of water to prevent the wrinkling. It was frightening to me to keep increasing the watering all the time, and finally stand them in water, but if I don't do that, the new growths wrinkle right away.

I might guess yours is getting too much light, or perhaps yours doesn't have many roots, so it can't supply enough water to the plant. I would decrease the light somewhat, and try to be sure not to let it go dry. If you have accordioning of the leaves, you can be sure the plant isn't getting enough water, but if this is caused by too few roots, you're in a quandry. If it's not too large a plant you might be able to enclose it in a large jar or an old aquarium to raise the humidity. I always keep my eyes open when I drive by yard sales for old aquaria for sale.

Mine lives in that or lower humidity. I am going to finally re-pot mine today or else. I am going to put it in a seedling mix as I have it in med bark and I let it dry out to much. But perhaps try what es suggests.

I am not getting any wrinkling of the leaves, I did when the pb were looking bad and I wasn't watering enough but now the leaves look normal they just yellow. A lot of the roots were desiccated and I left some that were questionable but I may not have a enough healthy roots. I did move it into less light, will see what that does.

can you post a pic?

If I were you I would go back to careing for the plant the way you did when it was happy and blooming for you.

Photos would help.

Sorry never posted pics, the yellowed leaves fell off and after I moved it to lesser light the yellowing seems to have stopped. Now I just hope I get blooms again.

I'll keep my fingers crossed for you.