that question is rather subjective. it depends upon the story’s pace, what kind of “secrets” you’re going to reveal, and the story’s general plot. there isn’t one magic episode when all the secrets can be revealed no matter what the story is about. like i said, the answer to your question heavily depends upon the plot. only you know what your story is about, so that part is really up to you.
i would recommend slowly building up the tension in your story and revealing the secrets one by one. for example, just when the reader thinks everything has unwrapped, another plot twist takes place. this keeps the story entertaining. if you just reveal everything at the end, the reader is likely to get bored of the story and abandon it before that. keeping the story interesting for the readers is critical when implementing plot twists.
there’s no such thing as a right time to start developing plot twists. you can start as early as the first episode and work your way up, or start building up the tension and reveal the twist around the middle of the story. the only thing you have to worry about is starting too late. if you don’t start building the tension from the beginning, the story will get uninteresting fast since episodes in which nothing happens have no meaning.
that’s basically everything important about “revealing secrets”. i hope you found this helpful & good luck with your story! 