Is using grammarly unethical(for rearranging grammar, using the right voice, etc)?

I am working on a story but I know it's important that the writing is my own and I don't plagiarize. I'm not providing any details on the story due to rule #3 and the little warning at the bottom.

If it's not a flat no, I'm really not sure where the line is between using something like grammarly and plagiarism. I could ask an LLM, but I figure they might be biased.