Slower ethernet speeds

So ive had my dlink router for about 3 years now and its served me well, never had any major issues. It handled my 500 mbps wifi speeds just fine. So now ive bought a netgear rax15 and although i didnt expect any improvments besides new hardware and maybe extra functionality. But somehow both my wifi and ethernet speeds have dropped from a 450 mbps upload and download average to 180 mbps and below. I know it sounds petty but if im paying for 500 mbps internet i should at least get what im paying for. Not sure what to do, new to netgear UI so i dont know how to go around flipping switches yet. Any suggestions.