From our friend Mr Elliot and Frost:
"Ending diagonal triangles indicate exhaustion of a larger pattern that moved too far too fast. Ending diagonals are usually followed by a quick thrust which retraces to the starting level of the diagonal."
This means that we would expect to see a quick return back up to the start of this, which was 11.5k.
I will now buy back in full when I see the end of this pattern.