An assumption is you are ...

An assumption is you are using two stage (treating the concentrate from RO 1 with RO 2) not two pass (treating permeate from RO 1 with RO 2).  A few thoughts.  Depending on the feed chemistry and pretreatment before the first stage, you may be able to blend some of the second stage reject back to the feed of the first RO and increase your overall recovery.  Treatment of the second stage concentrate may be another option.  A Nano system may provide the overall quality of the permeate to send directly back to the feed for the first stage RO.  Running at high recovery may provide what you need.  Another option is a high pressure RO system to produce a product to feed to one of the stages depending on permeate quality.  In both cases some pretreatment may be required to reduce the fouling load identified in the above chemistry.