Recent studies have shown that thematic change in fiction is driven as much by individual authors' choices as by generational succession: differences between author cohorts explain half the variance in novel themes. This paper examines the role of cohort effects in poetry, extending the analysis beyond vocabulary to poetic features such as meter and rhyme. We use Jensen-Shannon divergence to compare the rates of change across feature levels, identify periods of rapid change, and find the features driving them. Then we apply decomposition methods to estimate how much the features' frequency trajectories are explained by either cohort effects or within-career individual change. Our preliminary results indicate that topics and rhyme features are relatively stable over time, with about half of their variance explained by cohort turnover. Metrical repertoire, however, is particularly volatile throughout time and mostly shaped by individual change within poets' careers (58.7%).