Any reflection of "extreme oscillation" with retaken courses are the only situations id say briefly mention in your personal statement and i agree, leave the rest for the interview if it comes up. Keep it as positive as possible with what you can bring to the table. That being said, back in 2011 a Tornado took out my hometown while i was attending my undergraduate studies in hawaii. It took the lives of some of my friends and family members living in the midwest leaving me with no place to return too. For that reason, I had retaken my gen chem and molecular courses (F's) since i couldnt withdraw from my classes...however, next semester it all went to A's. If you have something THAT extreme ( rare incident for sure ) then it would be nice to counterpart that big of a fluctuation in your personal statement. You sound like your doing ok, and highlight positive goals and accomplishments whenever possible and convenient.