Coupling Transformers in a Bus Line
Just examining the 75 ohm and transformer connected to the 3k load, the combined impedance (assuming perfect transformers) is: -

75 ohms // (3k + 53.6 + 53.6) = 73.23 ohms

Clearly as you add more parallel transformers this number is going to drop so how do you account for the actual reading being a little higher: -


The transformer dc winding resistances will add a little
The tranformer leakage inductances will add a little impedance


Given what you have shown there can be no other reason other than your measurement accuracy is poor.