Some websites can not be reached by wifi on home network setup

[JimJoe123]

Here is my networking setup at home with many rooms that need wifi.
ISP router/modem, then (4)routers connected to ISP LAN1-3
ISP gateway 192.168.1.1. But room routers are 192.168.254.254. 192.168.0.1 (different from ISP 192.168.1.1)
Technically room routers DHCP should be disabled, but (2) room routers DHCP left enabled per factory setting.
Just for experiment, I gave all devices in rooms STATIC IP(192.168.1.xxx) with 192.168.1.1 as gateway and DNS1. 
This way don't matter IF room routers DHCP is disabled or not.
All devices got wifi and internet,  All HAPPY...

Then few WEIRD things happened..

First, all of sudden all devices can not get all websites. EX: can't get google or youtube but can get bank and speedtest websites. remember some room routers were still set to DHCP ENABLED. some disabled.
Then over night back to normal, access all websites,  I done NOTHING to network, except to got sleep.
Can anybody explain why some websites(google/youtube) were not available?
BTW even ISP router wifi connection did same(only some websites can connect)

Second, when connecting devices to ISP wifi (192.168.1.1), devices are getting 192.168.254.xxx or 192.168.0.xxx, something other than ISP gateway 192.168.1.xxx.
Is there some kind of feedback to ISP router from room routers with 192.168.254.xxx or 192.168.0.xxx ?
OR are devices (connected to ISP wifi) getting IP from whichever routers on network connects first?

The whole idea of testing wifi connection with STATIC IP on devices is to see IF DHCP really need to DHCP disabled always.

Any comments or discussions are appreciated

[deanwebb]

Why four routers? Does all this work when you have only one router on and active?

Also, if you have four routers, it reads as if two are on the first network and two are on the second - that means there are IP address conflicts. If the SSIDs offered by the routers have the same name, then it's even more confusion as devices get IP info from one router and try to send traffic via another and receive traffic from a third.