Scope Change- additional project to existing project

Dear all,

There is additional two new building project that was added to 6 existing building projects. the 6 building are almost complete while the two new ones are still in the structural stage.

The two new building contract were signed as an annexture to the main contract beacuse the value exceeds 20% of the original scope amount.

The existing  6 buildings project has a single baseline substantial completion of each building as a milestone with a cumulative 95% completion while the 2 new added building are are not included in the project baseline yet because the contract amount has just been finalised and signed.

Question

1. Do we re-baseline the 6 building project and add the two or maintain a seperate baseline program for the two new buildings considering the fact that its a single contract.

Note: the contractor has already started work on the two new sites with a tentative program being maintained seperately to monitor the progress.

The buidings are all typical .

Your professional opinions required please.