GND connections and ground plane routing?
Those are thermal relief connections to the ground plane to improve soldering. They won't create any problems as far as high frequencies go. You could change the settings in Altium to flood over those pads, whether that would create a solder problem depends on your board stackup and assembler's soldering process. I avoid ground planes on outer layers because they generally create broken areas of ground that could possibly radiate. Solid ground planes on inner layers are a better option IMO.