Here are some recent photos

What kind of bugs were you thinking could cause ? It has been inside since I've had it, so I didn't think about the possibility of bugs

Sometimes mites or mealies are very hard to see. You may not notice anything until your plant has been damaged. Like Rina said they favor tender new growth. And plants don’t have to be outdoors to sustain damage by either of these critters.

What do I do next? I've thrown fallen leaves from that plant in some of my other pots. Are all my plants in trouble now?

So after doing a bunch of research about spider mites and mealybugs,I don't think either of those pests are the problem. The white/Brown areas are hard and not cottony. I also haven't seen any insects. I was thinking maybe it could be a sunburn, but it began happening before I moved the plant.

You say the plants were originally in low light. Did you wean the plants into more light? If you plunked them into strong light they could be burnt. Generally, that would impact more than new growth, but it's a thought.

Another thought - I can't see the leaves closely, but I am wondering if they were over watered at some point and burst (for lack of better description) These marks on my plant are larger, but you can see how the "stretch marks" look on these leaves. They are white marks.

Good luck!