If you double the speed of a pump you will need eight times the amperage. The increased amperage can be caused by a change in the product. The motor was sized for a low specific gravity fluid, but the lines are being flushed or tested with water. The specific gravity of the fluid has increased for some reason. The viscosity of the liquid is increasing with a change in temperature.
Some viscosities increase with a lower temperature, some with a higher temperature.
The viscosity of a liquid can increase with agitation. That is how cream becomes butter. The increased amperage is caused by two part rubbing together as a result of shaft displacement. A bent shaft. The rotating assembly is not dynamically balanced.