The important graph is the first one: the number of pages crawled per day. And that one doesn't seem to have changed significantly, apart from day-to-day hiccups. It looks more as if, over the last few days, they've been randomly crawling your smaller pages. Look at the "time spent" graph, and now compare the red graph and green graph. You'll see they are essentially the same shape.
Now go down a few tabs and look at your Index Status. Any worrying changes there?
If you've done things to improvement performance and page load, then that can decrease. Things like minimizing and combining scripts, enabling compression, etc have had big impacts on it ..in my experience.