Why the sudden drop today relative to peers (and over the past...

Why the sudden drop today relative to peers (and over the past week) when the fundamentals seem excellent - ie high prices, low $A, high quality product etc etc?

There's a lot of volatility in the movement of the share price for both NHC and WHC and it's usually reasonably closely linked to the selling price of coal around the world. About one month ago, the Newcastle coal price was sitting at around $US150. This morning I noted the price sits at $US123.50.
So that represents about an 18% drop in the Newcastle coal price across the last month. The NHC share price has dropped about 14% during the same period.
If you compare the drop in the SP of NHC with WHC across the last month you'll see that it's fallen more but almost certainly due to the transition of NHC to ex div during that time whereas WHC went ex div about a month earlier.
If you compare the two SP's across the last three months, which then encompasses the ex div moments for both companies, you'll see the drop has been almost identical.
A few days ago, after the WHC announcement of the takeover of the BHP coal mines, the WHC share price suffered and there's been a bit of a correction to that overreaction across the last two days.

Of course, it's all a little more complicated than simply following the Newcastle coal price but when you see a strong movement in the SP, that's a good place to start looking.