Why do you call it a coffee cup plant?

http://www.finegardening.com/coffee-cups-elephants-ear-colocasia-esculenta-coffee-cups

Okay, I understand lol!

I thought maybe it was planted in a coffee cup. If that were the case then I'd have an answer for you, sorry I can't help.

What kind of soil does it have? What size pot is it in? Can you get pictures of the whole plant?

These originated in Thailand and were called "Tea Cups". They tissue cultured it to retain the characteristics and then exported around the world. Sellers in the US changed the name for marketing it, as something new and exclusive. There's something like around 2,000 varieties/cultivars listed for Colocasia esculenta, so plenty of choices.

These like to grow in shallow water and they don't like it cold. Leaves will age and wilt. You say the rest of the plant is thriving so there might not be a problem. A photo of the whole plant would help.

Actually I've come to the conclusion that tea cups are dwarf(to about 4') and coffee cups get much larger, it's been an on going debate between myself and a few other growers, otherwise they are identical!

Now! The real question is the health of the plant!

I can't see well enough on my my tiny screen to say for sure... But I see sign of mosaic virus, DsMV, it's untreatable and highly infectious!

This is generally a bad time of the year to be paranoid, in fall it's perfectly normal for leaves to turn, and strange, bad looking marks to occur on leaves of all plants, especially colocasia! So don't freak out yet! But please do some research on DsMV and if you really think that's what it is, destroy the plant! Do so with care, as you can very easily spread the virus to other aroids.

If the discoloration is white, or creamy white, it's bad news! Especially if it's feathering out from the veins, as it appears to be. Again, I can't see well enough to confirm or disconfirm mosaic.

Its become quite the scourge!

Best of luck.