Make sure your devices are only using Pi-hole. If they have another DNS listed, some of their queries will be sent through the other server and won't be blocked.
root@DiskStation02:/# cat /var/log/pihole.log|grep theage.com.au
Oct 27 21:46:12 dnsmasq[26061]: query[A] www.theage.com.au from 192.168.1.151
Oct 27 21:46:12 dnsmasq[26061]: forwarded www.theage.com.au to 1.0.0.1
Oct 27 21:46:12 dnsmasq[26061]: reply www.theage.com.au is <CNAME>
Oct 27 21:47:27 dnsmasq[26061]: query[A] www.theage.com.au from 192.168.1.151
Oct 27 21:47:27 dnsmasq[26061]: forwarded www.theage.com.au to 1.1.1.1
Oct 27 21:47:27 dnsmasq[26061]: reply www.theage.com.au is <CNAME>
root@DiskStation02:/# cat /etc/resolv.conf
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
# DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 1.1.1.1
root@DiskStation02:/# cat /var/log/pihole.log|grep theage.com.au
Oct 28 11:11:32 dnsmasq[26061]: query[A] www.theage.com.au from 192.168.1.151
Oct 28 11:11:32 dnsmasq[26061]: forwarded www.theage.com.au to 1.0.0.1
Oct 28 11:11:32 dnsmasq[26061]: reply www.theage.com.au is <CNAME>
Oct 28 11:11:32 dnsmasq[26061]: query[A] www.theage.com.au from 192.168.1.151
Oct 28 11:11:32 dnsmasq[26061]: cached www.theage.com.au is <CNAME>
Oct 28 21:39:52 dnsmasq[26061]: query[A] www.theage.com.au from 192.168.1.151
Oct 28 21:39:52 dnsmasq[26061]: forwarded www.theage.com.au to 1.0.0.1
Oct 28 21:39:52 dnsmasq[26061]: reply www.theage.com.au is <CNAME>