All three of those sentences are declarative statements. None are questions, and none contain a question. So, each sentence should end with a period, not a question mark.
This is a common error made by native speakers in writing, because the intent of each statement is to get someone to respond by providing information, the same as a question. But each sentence makes a statement of fact and leaves the questioning intent to implication.
The following might illustrate why these are declarative statements and not questions.
I was wondering if he is from California. But when I saw his driver's license, I stopped wondering.
I'm not sure if that's the right solution. And please don't tell me.
I'd like to know if it's OK to put a question mark after an embedded question. To find out, I'll ask on ELL.
If you want to explicitly turn these into questions, you could write:
I was wondering, is he from California?
I'm not sure—is that the right solution?
I'd like to know: is it OK to put a question mark after an embedded question?
These sentences really do contain questions. You can tell by the altered word order. As you can see, the answer to your question is actually yes (depending on how one defines "embedded question").