i can't really get a feel for differences in the pics above just because of the angles and lighting but it is pretty common for hair to change over time (whether because of length, care or styling etc.)
Mine loosened with length (weight of hair), products used and style (can make it wavy or tighter depending on product or style I wear). Also, I just started henna-ing. I have heard that loosens curl too.
I think this is pretty common.