Hey guys, thanks for you replies!
I am using the default PLA temerature settings (210C with 60C bed). And yes, I was using the default print speeds in expert settings.
This makes a lot of sense now, as I upped the layer height of the "fast print" settings to 0.3 from 0.15, effectively doubling the amount of material I'm asking the printer to extrude at the same speed. Top/Bottom thickness was also set at 0.6mm which is only 2 layers so that was probably part of the problem as well.
I was trying to get a fast print, but I guess I got too greedy. I'll try again with a slower speed/ lower layer height, and increasing the top/bottom thickness and see if that solves it. Thanks everyone!