lets see the whole plant.. including the pot..

give us a precise history for the last year.

and fully explaining how much light it gets ...

have you tried wiping it down with a damp cloth ...

ken

@ken_adrian Adrian MI cold Z5Z5

The plant receives indirect light all day and I water moderately when it's dry which is about once every 2 weeks. It's been in this same spot forever and conditions haven't changed that I'm aware of. Aside from these white patchy areas I've also lost a lot of lower leaves and they turn half yellow before dropping. Here's a picture of one of the dropped leaves.

Yes I've tried wiping the leaves with a damp cloth but hasn't helped. The white patches appear to be "in" the leaves for lack of a better word.

Thanks for any advice anyone can provide.

@Tina Fung The white marks are mineral deposits from using water with a high mineral content, or the result of using a pot that doesn't allow you to flush the soil regularly. When you aren't flushing the soil as you water, dissolved solids (minerals and salts) build up in the soil and eventually become so concentrated the plant is unable to take up water and nutrients efficiently. A high level of dissolved solids in the soil solution can actually reverse the flow of water into cells, pulling water OUT of cells by way of the same mechanism that curing salts pulls water from cells of meats like bacon/ ham/ jerky. You can try using a mild solution of distilled water with some vinegar or lemon juice, but it might not be effective. The fix is to use a different pot so you can flush the soil when you water, and/or start using distilled or R/O water. A R/O system can be had for about $300, and you can install yourself in less that a half hour ..... 10 minutes of actual work. The R/O system produces water with 0 ppm dissolved solids. The right system removes chloramine and fluoride, and makes great water for drinking (especially coffee) and cooking.

Your plant shows it's dealing with other serious issues as well. It's likely over-potted which would mean it's being over-watered, it doesn't like the pot it's in, it's not getting even half the amount of light it wants, and I'm wondering about how you're supplementing nutrition (fertilizing)? If you have interest in getting the plant back of track and want to make a plan, just ask. If you live in the US, mid-late June is the best time to tackle a repot, but there are some things you can do before to help things go smoothly.

Al