Increasing throughput for nrf52832

We are using nrf52832 with S132.

In our application, we have 1 device as central and it will connect to 4 peripheral devices.

Central device needs to send 128 bytes of data to each of 4 device at interval of 30 msec.

We have extended the data length to send 128 bytes in 1 packet.

Currently we are sending these packets at interval of 100 msec and still packets are getting dropped.

Connection interval is set to 7.5msec.

So how can we increase throughput to achieve our requirements?