ASINS suppressed due to competitor buying and returning my products

I was selling in a relatively new category which had no competition for the past 12 months. My return rates were 4%. However in the past 2 months my return rates have increased beyond 12% and Amazon has suppressed some of my listings.

At the same time there is a bigger competitor from a bigger category who has launched a product similar to mine and the timing is just too suspicious.

I believe they are using fake accounts to buy and return my products. And now my ASINs are suppressed. I have no proof for this theory other than my previous return percentages. The quality of manufacturing and the quality of the products are the same as before. How can I fight this?