Ianklarkara Cheyenne Marie Green Gecko with Yellow Mottled Leaves

[dianecty]

Hi everyone! I was wondering if you could give me some advice about my Ianklarkara zygopetalum named above. I bought it a few months ago and it had light green leaves with a few tiny brown spots. Now the leaves are big and long but they suddenly became mostly yellow mottled with green on both sides of the leaves. Otherwise the leaves are firm and healthy and the pseudobulbs are fat and firm.

What's wrong with the leaves and how do I fix it?

Thanks