You need to switch to Linux and you can get 25MH/s, for another day. Then maybe 22-23MHs or so. If you are using Windows the speed will even be much much worse especially the higher that the DAG goes because Windows need more GDDR cached used up, Linux uses much much less.

You really aren't missing out. Profits are "ok", with $0.10 power the most you make is like $0.70 a day. So unless you got tons of these GPUs in your farm, just not worth the hassle to learn how to use a new OS just to get 1 GPU running for another couple of weeks. Best is to try and found an 8GB varient of the RX 470 and buy that instead and then you would get your 30MH/s speed back and the GPU would be worth more.