It looks under-fertilized such that the darker green areas are closer to the norm than the rest of the chlorotic foliage. What have you been doing to supplement nutrition (fertilizer)?

Al

I didn't fertilize it yet, I wasn't planing of doing it, but I definitely will, thank you!

I'm pretty sure that's the problem. Let me add that all fertilizers are not created equal. Foliage-Pro 9-3-6 is a superb fertilizer for close to all of the plants houseplant care givers are likely to grow. It has all nutrients essential to normal growth (few soluble synthetic fertilizers can make that claim), in a ratio that favors your plant, and it doesn't get it's N from urea - an attribute that helps keep you plant full and more compact. It's the only product you would need to cover the full spectrum of essential nutrients; and, it's worth the wait as you'll likely find you'll need to order from an online source.

Please come back a couple of weeks after you fertilize and let us know how you've fared.

Al