Newer leaf turning yellow??

[Zekeyflower]

I have an oncidium that I've owned for about a year and a half that has never bloomed since I got it. It is my first and only orchid so at the beginning I wasn't taking care of it correctly. More recently it seemed like it was doing very well.... I found a nice spot for it where it gets a good amount of light and it grew a new psuedo bulb, yay! It is also starting a new growth which I am assuming is going to be another new psuedo bulb. So I finally felt like this plant was thriving.... BUT now it has two yellow leaves. One of them is from an older psuedobulb so I'm not super concerned about it, I think it's just running its natural course. But the other is from the newest psuedobulb and I'm not sure what is going on. I don't feel like I over water them at all. If anything, I under water them. My psuedobulbs tend to get wrinkly and the old ones are super wrinkly. So I don't think it's root rot. So now I'm concerned about the possibility of pests or a disease. I just don't know why a leaf that is less than 1 year old would turn yellow so fast. At the same time, the new growth that is going to be another psuedobulb looks great. Anyone got any ideas what is going on? Please help! I am including pics. First pic is of the oldest leaf that's turned yellow, it had been sunburned it the past so it looks pretty bad. The second is of the new leaf turning yellow. The third is if the new growth. Fourth and fifth pics I included to show the roots. I took these pics after I had just sprayed the roots with water.

[Orchidtinkerer]

I wouldn't worry too much.
It looks in very good shape, oncidiums do pull reserves from older leaves when they are producing new growths or flowering. The remaining leaves look great, lots of new roots are forming and they are looking healthy so I personally would not worry about this.
My dendrobiums are shedding their leaves, its that time of year, could also be that, my oncidiums have dropped a leaf each also.
Just carry on doing what you are doing, it seems to be working

[estación seca]

I think your plant is severely underwatered, and not getting enough light. Pseudobulbs of healthy Oncidiums remain shiny, fat and smooth as long as they survive. Wrinkles indicate water stress. New growths become at least the size of previous healthy growths before a pseudobulb becomes visible.

They flower best with enough light to be light green.

I would suggest giving it more light. Water so it never dries completely at the roots. It will take 2-3 growth cycles to recover, but you might have flowers sometime in spring-summer 2021.

[Zekeyflower]

Thank you for the input guys 😊 Im gonna adjust my curtains so that it gets more light and keep a close eye on it the next few days.