Try reducing the line width especially for the initial layer. I googled about Arachne line generator and it looks like it’s the default wall generator in PrusaSlicer as of v2.5. I can’t tell if you’re using a textured build plate or not but you could also try swapping to a smooth one (or vice versa) and seeing if that makes any difference. You don’t even need to print the whole tab for testing, just the first few layers to see if you’re on the right track.

You could also try using a 0.2mm nozzle just for the white filament and seeing if that helps.