Dear @applepies,

I need to increase the ip address for my company future upgrade.

So the current setup is 

Unifi router - load balancer - Firewall - Managed Switch

I would like to change the current subnet to increase the amount of ip 

There could be multiple DHCP servers in your current network.

Usually, the router such as TP-Link TL-R470T+ would work as a NAT device and a DHCP Server by default settings.

And some Managed Switches can work as a DHCP Server after configuration as well (normally the DHCP Server is disabled on a switch).

I find that changing to /22 or 255.255.252.0 But the question is which devices is handling the ip range?

Because the switch broadcast 10.10.10.1 ip where the unifi is broadcast 192.168.1. Is it i need to change the unifi router subnet in order to increase the subnet that the load

balancer can provide??

To know which device is handling the IP range, you could check the IP address and default gateway obtained on your clients. If the IP address and default gateway are 192.168.1.x, then the unifi router is handling the IP range. Please note that it doesn't mean that more clients can be connected to the network after increase the IP address, we need to pay attention to the actual capacity of the gateway in the network. Take TL-R470T+ for example, the recommended number of connected clients is ~30 to ensure good performance.