Appears to be too wet. And it needs to be repotted too.

Might be kept too wet as Harvey said. You also need to be careful about water quality and over fertilization.

You don't state where you live, how long have you had the plant, where is it growing and how do you take care of it. Hard to give advice without a background.

If you are in a warm climate or grow indoors, give us more info.

The plant looks healthy except for the newest growth. If the plant gets good light, maybe you are overfertilizing?

Provide more information about where you are, climate, etc.

Jane

over fertilizing might be a issue as my tap water is very hard and i add fertilizer to it..... and yes my climate is warm and I am experimenting on growing indoors where i can control the parameters easily whereas outside my temp. gets very high or low drastically... I repotted my tolumnias into a terracotta pot with some bark as i had hydration issues and I also seemed to not have enough light so i bought a LED 18W spotlight and kept it above them. and... do you guys have any tips on repotting the oncidium should i replace the medium or should i just add new medium around the old.. what size pot should i use...BTW my room temp. normally is around 28-30 celsius and if it exceeds that i could turn on my AC

the're near a east facing window with reasonable indirect sunlight...

I am in south India... Chennai to be specific