Nope, not unethical. They are still your stories no matter what pen name you use. In your new profile, you might, though, note that you previously published here under the previous name. Than, if someone challenges you on stealing someone else's story (even though it's your own), you can point to the profile notation.
"I don;t spend time checking on what other people are doing, I just worry about my own shit." -- Lovecraft68
"although I may come across here as somewhat abrasive at times I respect people's efforts and take feelings into consideration." -- Lovecraft68