Good to hear milad give it some time you'll see improvements soon
as for nitrates, is your ro running right ??? Is your skimmer before your return pump in your sump??
I had 40ppm in my tankhad me worried so I increased my water changes to 5% every 3days, pretty much starved everything for a month and now I'm back under 20 . Lots of flow and turnover as someone said have a powerhead close to the top aimed up at an angle just to the point where bubbles don't appear, your goal is to have no water lay still and provide lots of current to your skimmer
have you tried fiddling with your skimmers tuning to achieve a better skim????
Good luck my friend