subnet bridge

Hi, had a strange (or not) thing happen recently on my home LAN.
wanted to get feedback.

background:

ISP modem (cable internet) providing DHCP on subnet 192.168.0.1.
Fed into 2 APs via ethernet ( with static IPs in each) 192.168.0.100 & 192.168.0.200.
DHCP pool was 192.168.0.150-192.168.0.199.

Each of these APs where actually routers setup as APs as per the guide on the SNB site. one was an asus rtn56u, other was a tplink archer.(running ddwrt)

anyway, i got a new ISP. It's modem was...

subnet bridge