If you're going to use Flourish I can't see the need to continue will CSM+B. I would dose 10ml of Flourish 3x/week. Fe you can continue to add if you want and I'd try 1 tsp of GH booster once a week. Just based on EI recommendations you need to double the amount of KH2PO4 to 1/8 tsp and possibly more if you're still seeing a lot of GSA. Just keep an eye on your circulation and CO2 also.
In addition to water changes you might consider using some Purigen in your filter to get rid of the the dissolved organics.
In addition to water changes you might consider using some Purigen in your filter to get rid of the the dissolved organics.