I think this review may answer your question. http://thermalbench.com/2016/07/12/corsair-ml120-pro-120-mm-fan/
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Rated at 0.225 A (2.7 W on the 12 VDC rail) for the ML120 Pro non LED and 0.299 A (3.6 W) for the ML120 Pro LED fans, these should be handled appropriately when it comes to powering multiple such fans. In practice, these fans drew an average operation current draw of 0.131 A (1.57 W) for the ML120 Pro non LED and 0.172 A (2 W) for the ML120 Pro LED fans each and a single 1 A motherboard fan header will be able to power them easily- perhaps even 2 or 3. A powered PWM splitter is recommended if using 4 or more fans on the same header, and there is another reason to keep 3-4 fans per header as it is which we will get to soon.
So 3 should be fine on one header. It seems the power draw, in practice is, less than stated on the back of the fan. It may be the start up current draw that is labelled.