When I started mining here in late October I was getting .5 BTC daily. I thought the network and diff grows to a certain rate, right? I never remember getting .3 .4 ever, it just dived to .1 and stayed there. It basically jumped from .5 to .1 pretty much skipping all the numbers in between. Where did those .3's and .4's go? I would have loved to see them.
You clearly weren't paying attention. The network difficulty has been going up by roughly 20-30% every 10-11 days since October. Your earnings have similarly declined regularly since then. On a day to day basis they've gone up and down wildly (look at the luck chart which shows the last 3 months of luck per shift), but on average, each 10-11 days has been earning you less than the 10-11 days previous.