No Key Fragments for a Week

Recently, I've noticed an extreme scarcity in the amount of key fragments I get - and by extreme scarcity, I mean 0. I have earned 10 key fragments (3 chests worth and 1 extra) since the system opened and got decent drop rates, maybe 1 every 4 wins, at the start. Although I know that they become harder to find as more are dropped within the month, it seems odd that I haven't gotten any at all for the past week, in which I've won roughly 16-20 games, all ranked pre-mades ranging from 2-5 in the lobby. Is this radical decrease in key fragment drop rate normal, or am i simply unlucky? My premade friends continue to get drops every 4-6 wins consistently and have overall earned many more than I have.