Hi,
It's difficult to say why the earnings have dropped. I've had a look at your account and it seems that you have a lot of Malaysian traffic. I'm not much of an expert on traffic from that region and I don't know much about the bid prices on keywords there. It is clear that the PPC on your domains has dropped from October to January and February doesn't seem to be picking up much. I can't really say whether this is because Google are paying us less for traffic from that region or because the bid prices are lower.
I would imagine it is because the bid prices are lower. Why? From November, Yahoo started pulling out of markets where they had no chance against Google In all, they pulled out of over 30 markets, leaving Google to rule the roost. Naturally, with Google the only place for bidding, the prices have slumped, as many have mentioned with international traffic on Yahoo feeds.
Without knowing much more about the market, I would suggest that this is why the PPC has dropped.
Ed