Your orchid is some type of Oncidium. Oncidiums need a lot of water and a couple of hours of morning sun, and then bright for the remainder of the day!
Your orchid is not getting enough water!!! The media, bark mix, is too coarse. It needs to have fine particle size so it can hold more water. Compared to many orchids that have robust, thick roots, the Oncidiums have very skinny roots. They need a fine mix to grow in. Adequate moisture will make the entire plant grow larger but when it grows with a water deficiency, it just limps along never really looking healthy. Those bulbs should get to be almost as big as a tennis ball and produce multiple flower spikes per bulb.
Fertilize half strength every other month.
Lastly, Oncidiums do not hold onto their leaves for ever, 2 years maximum so you can't expect leaves to look pristine for ever. They naturally yellow and fall off. It is normal.
Their leaves have a thin substance to them and are easily subjected to false spider mite damage. Those damages can lead to fungal spots on the leaves.
