Start by finding what the actual chainline is. You can do this empirically by measuring from the chainrings to the downtube and adding half the diameter of the tube. Then compare to the standards or to the cassettes chainline (distance from inside of dropout, subtracted from the dropout width).

You can also measure it directly by placing a straightedge (edgewise, not flat) on a secant against the outer chainring, and carrying it back to the cassette, then allowing for the offset to the center of the chainrings seeing where it compares to the center of the cassette.

Based on that, you can decide if you're best option is to move the cranks outboard, check rear triangle centering, increase chainring separation, or use a narrower chain.