Decreasing Reviews After Linking Product Variations: Need Help with Amazon Vine Program Issues

I sell one product in multiple colors, and initially, I didn't link them as variations. I applied for the Vine program for each color, paid Amazon, and sent the products to customers to receive valuable reviews.

To my surprise, I found that several colors were sent to the same people, who then left reviews for different colors. When I opened a case and asked customer service, they replied that this was normal.

I then linked the variations together since they are essentially the same product, just in different colors. However, my reviews started to decrease after this. Opening a case didn’t help, as I only received canned responses. Has anyone else experienced this issue? How did you resolve it? Thank you.