In PrusaSlicer, go to Printer Settings -> Extruder 1 and reduce the retraction length to 0.5mm for PETG and 0.3mm for PLA

These values are only a starting point and you will need to adjust them later according to your tuning

The Hemera has a much shorter filament path and efficient cooling tha original Prusa extruder. If your retraction is too long you might clog the Hemera

This setting might be overridden by your filament settings, make sure to check them