Tire wear in the middle to inside on rear

[Hatsuongmai]

I had four Bf Goodrich tires with swift and SPC rear camber kit for around 16k miles, but now the rears are ball. The rear tires wear most in the middle and toward inside as show in the pictures. I got my alignment done when I installed those tires and it was within spec. at the time. Is this caused by toe problem or something else? I know it's not over inflated problem because I always ran those tires at 35psi. Does anyone have this problem on their car before and what was the solution? Thanks.

Rear Driver side:

Rear Passenger side:

Front Passenger and driver: