I'm getting the message below everywhere I attempt to access weekly or monthly hiscores.
I first noticed this message popping up around May 15th on the regular hiscores.

One funny thing I did see when the hiscores failed was my script parsed an error through as the hiscores count: 108,800. I noticed the 108,800 value going back the last several days, and I removed those from the data. You can now see the last good value was roughly around 50,000 accounts on the hiscores this morning.
When the hiscores updated yesterday night, I saw the 108,800 problem become much worse than it had been the last several days. Around 10 AM Central this morning, the weekly and monthly hiscores became inoperable.
This is entirely a problem on Jagex's end, and there is not much else I can do until the hiscores start returning usable data again.
One thing that I did on the site was make it so that now you can click on one of the OSRS activities below and it will give you the same chart at the top that you would see for a particular world if you selected it. So now you can take a look at Leagues and see how it performed over a certain period of time.

The hiscores are broken. There is a hiscores outage today. And as the man himself, Shaggy, once said, it wasn't me.