There is no way you can be 100% original at this point. Literature has existed since looooooong before and pretty much everything has already been written. That doesn't mean you can't write literature though. The best we can do with so many centuries of literature before us is to try and be unique, timely, and exploiting new ways of writing to be original. I feel like that is the top thing I want to try with my series at least, but I don't look at the details like "my character is an orphan, therefore, I am ripping off other stories with orphans as main leads' just as example... Looking at literature like that would mean that nobody would be allowed to write. Plus, inspiration does not equal ripping off, even IF you are basing it off something (which in your case you said it was a coincidence anyway).
One of my favorite examples of this is Hunter X Hunter the anime/manga... Now I'm not saying they rip off anything, I mean obviously not, but it is a shounen Manga. Now we all know what a shounen Manga is, right? They are kind of similar in theme but that doesn't mean they rip each other off. But HxH has a very bland look to it from the start. When you start reading, you literally think to yourself "i've seen this a hundred times before" but I believe it was done on purpose by the author as quite quickly you realize while reading just how wrong you are with your assumption. It seems to me like the writer does everything in his power to "deconstruct" the shounen formula. (for example, the main character changing into a bloodthirsty monster, while the monstrous villain turns into a sympathetic guy, also, please watch HxH, it's the best show ever)
And the reason why I talk about that is just to show that that's how you make good writing nowadays. You don't (because you can't) create original ideas, but the best you can do is "deconstruct" established ideas and make it your own. Hope this helps at least somewhat. Even if it's long, I'm just writing all this because I really don't agree with the whole plagiarism in many cases in story-telling (unless the evidence is too overwhelming of course) and what you describe seems to be as an innocent coincidence, and instead of wanting to change what you write, I suggest expanding on it and make it your own. I do suggest looking into the stories that you found as similar to yours further though, just to help you expand on them too.