Did you post your pre-print on SSRN? Having a date posted from SSRN allows you to stake a claim for your idea with a third-party verifiable date. As noted above, ideas can be common but research is usually not.
At SSRN, we have had a couple of papers over the past 15 years that were
very similar to other papers. When we were notified of the similarities, we contacted all of the authors and they resolved the matter VERY quickly. If you need help or have any questions, you can contact SSRN at:
authorsupport@ssrn.com or 877-SSRNhelp
Assuming the moniker as accurate, you just received a response from Gregg Gordon, President and CEO of SSRN. How the internet Gods managed to bless you with a response right from the top I will never know. This is a reply you should take seriously.
I only have your post to go on, but I don't seen enough here to raise alarm. The framing and conclusions are different. The papers originate from different fields. Sometimes interesting questions get addressed by multiple people concurrently.
Personally, I've had this happen to me two times. The situation is not the same as yours as the two papers were ahead of mine in development were essentially asserting the same research claim as I was. Each time I had through of the idea, the methodology, and results in a similar fashion independently of these papers.
This happens. There are a lot of researchers out there working on similar material.