Starter improvement question & photo

I bought the KA starter about 8 weeks ago, got it going well, and it produced good taste results. I always keep it in the fridge, after I leave it out for 4 hours or so after a feed.

At about the four-week mark, with at least twice-weekly feeds, I started getting really excellent flavor in my loaves. Prior to purchasing the starter, I had baked bread only with commercial yeast, but I can't imagine doing that any more. It seems like the flavor the starter imparts to my loaves has improved week by week; I'm certainly not doing anything else differently. My crumb has lovely holes now. I'm somewhat amazed at my results, because I've been somewhat imprecise in terms of maintaining my starter ratio of original/addition, I've fudged a bit on my dough refrigerator retard times, and I never feed the starter the night/day before mixing dough.

My question for the chemists in our midst is, to what can I ascribe the improvement in the flavor of my loaves? Is something chemically changing with each feed? After this short time with my starter, I can certainly see why people grieve when their long-held starters die.

Below is the dimly lit result of my voluminous bake yesterday: KA extra-tangy sourdough baguettes and poppyseed pain d'epi, and SJ sourdough. Lots of happy recipients! As a side note, one of the grignes actually cut the top of my finger...I didn't realize they were so dangerous! ;) . Note to self: angle those epi leaves out more sharply after they're cut. 

Carmen