What do these spotty leaves mean?

[bunni1223]

Hello! First time posting here and I´m new to bonsai and currently loving it.
I own a Sageretia theezans and it´s growing pretty well, but lately I have been spotting some weird leaves among the normal green ones (second pic is how it generally looks). They have these spots on them but are not as frail as dry leaves.



Some info that might be useful:
Lately the weather has been very cloudy and it rains a lot in here, I tend to water twice a week. The nights can get cold. The tree does not have shortage of leaves, in fact there´s A LOT of leaves. I haven´t seen any bugs in either of my bonsai. I keep it in my balcony and in the afternoon it faces the sun. What does this mean and is there something I need to do/change? Thank you for reading.

 

[Shibui]

Really difficult to accurately diagnose problems from online pics.
The damaged leaves could have some fungal infection or possibly nutrient deficiency but the tree looks very healthy so I'd say nothing to worry about unless it becomes more widespread.
Another possibility is those are older leaves reaching end of life. Even on evergreen trees, leaves still have a finite life - usually 2-3 years After that they are not as efficient so the tree drops them in favour of the younger, more efficient leaves. If the affected leaves are all from innermost branches this, or lack of light, is likely to be the answer.

BTW, many aspects of bonsai are related to time of year and local conditions. Adding a location to your profile can give us valuable clues that might help solve problems better.