Variable UDS allocated by builder for same size apartments.

I have bought 2BHK (1143 sft) property from Builder in Aug 2011 and got 33% (385 sft) UDS in sale agreement for my 2 BHK flat. Later in July 2014, i had to go for upgrade to 3 BHK in project due to construction flaws in my apartment and upgraded my flat to 1520 sft(3 BHK) by paying difference cost at current rate. During agreement signing,I did not notice that my UDS was reduced to 30% and now agreements is signed (Agreement dated: 11th Aug 2014). This reduction was due to construction of new apartments by builder without informing buyers in the property for which approvals came (29th sept 2015) after signing agreement i came to know about this UDS reduction when i planned to go for registering the sale deed. Now, when i am asking for UDS calculation, builder is not providing the calculation and not agreeing to modify the sale deed. I have few queries- 1) Can i take this legally in court of law for compensation for wrong doing by builder after sale deed registration? 2) Can UDS differ for same size apartments? 3) Since Sale agreement was registered before new apartments approval, can sale agreement be termed legal with new reduced UDS. Can i fight in consumer court?