Ok the following is jmo, but it's what I would do if it were my tank
1. Cut down photoperiod (I know what you said earlier but it will help)
2. Reduce the power on your white channel a little more (blue too if it has any colors besides blues)
3. Reduce the amount I was feeding, and I like to feed NLS pellets once a week because it's very easy to only feed what the fish will eat by feeding a pellet or 2 to a fish at a time 3-4 times waiting in between for them to completely eat the pellet, I feed different frozen foods the other 2 times I feed a week.
4. Ditch any pads or sponges being used and replace with a media like purigen and phosgaurd (sponges and the like make me wary, I do use poly fill for filter floss but it gets tossed weekly) as they're more efficient
5. Rearrange the power heads so one is pointing at the worst of the problem areas.
6. Check the tds
of your ro
unit, may be time to replace the filters/membrane.
7. Assuming your ro
unit is good you may want to do bi weekly wc
's for a while.
And now a couple more questions, were you using 2 korillia 650s or was that total gph
, and what test kit are you using for nitrate phosphate test?