I suggest you and the other concerned owners write a letter to the Committee and the strata manager setting out your concerns, including what you believe is the improper removal of the palm trees from the common property.
You should then state that any changes and work of this kind must be approved through the appropriate processes, which may include the approval of the owners in a general meeting. You request immediate confirmation that these processes will be followed and until this occurs any further work will cease.
It is odd that they removed what sound like mature palm trees without any Council approval.