DNS Filter Servers 173.243.140.53 14,030 ms !!!

Hello, I started expereincing slowness in my web surfing in the last couple of days, and after a few checks I found out what I wrote in the title.

a few details on my setup:

Fortigate 200E running 6.4.1

the dns servers are cloudflare 1.1.1.3 1.0.0.3

i found in the cli reference that you can change the address of the SDNS, but nothing i did can actually work. i always get:

command parse error before 'sdns-server-ip' Command fail. Return code -61

how can i change that IP? i want to test the European IP for the DNS filter server.

thanks!

EDIT: it gets worse, it is now "unreachable"