Probably mostly to do with the weaker than expected China May PMI. Although with seasonal adjustments it was still in line with April's number apparently.
From Goldman:
"China’s official PMI softened to 53.9% in May from 55.7% in April.
However, since the PMI started in 2005, its May readings have consistently been lower than its April readings.
After adjusting for this seasonality, the May reading was slightly higher than its April reading. Therefore, we would
not view the softening in the headline PMI as a sign of much softer industrial growth in May."