Contrast in the mode of Sylvia Plath's works

In October of the year 1962, Slyvia Plath wrote a few works concerning the Holocaust, specifically Daddy on the 12th, and Lady Lazarus on the 23rd.  Although both concerned the horrid times of a Jewish life, the mood of the works are quite different.  Wasting no time, Plath sets the mood of wild anger in the 1st line, seeming so furious she was flustered.  As opposed to Lazarus, where she cooly begins, "I have done it again."  Very calm and composed, she flies through the beginning part her work with much clarity and even slight humor, very at peace with what life has handed her.  This discrepancy in mood is not what is interesting to me, as writers especially are known to have up and down moods, but what is interesting is how the moods change so drastically mid poem.  As confused and upset as Plath is at the start of daddy, she is equally focused at the end, realizing that it is her father who the anger is directed at.  And the once light writing in Lazarus quickly turns dark: "I do it so it feels like Hell" and "Herr God, Herr Lucifer."  I am not sure where I am going with this per say, but I am curious to see what happened between those 11 days which would have led her mood to change so much.  I would be curious to see your thoughts.  Thanks.  Tyler