Broadcast speed with XBee Pro S3B

I have a network of 7 nodes(1 master, 6 slaves) using S3B devices that I use sendBroadcastData() to send packets of 20 bytes at a time. I benchmarked how long the sendBroadcastData takes to return (not the network time) and find that it takes in the order of 350-800ms per packet. That seems a lot of time for so few bytes. Is this normal or is there something that I need to adjust?

I did play around with the serial baud rates and on air baud rates but this did not have any significant effect.

Alternatively, I can rewrite my Java software to use sendData() if I am sure that this will increase the speed that I can send messages.

Any links to benchmarks would be most helpful. Thanks

I would suggest looking at the NH and BH commands in the XBee PRO 900 HP product manual.