Is my battery swollen? (Macbook Pro retina Late 2013)

I just opened my Late 2013 retina MacBook Pro bottom case to blow off the dust it accumulated. It was relatively clean inside, but battery caught my attention.

I suspect it begins to swell. Hence my question - how does healthy battery look like? Should it be perfectly flat blocks? Another thing that raises my suspicion is that back cover does not fit perfectly when laid relaxed. I need to screw it to the case to align with rest of the body.