Yeah I noticed this too and it could be for many reasons...
HubPages changed their Adsense layout and there's no way of knowing if it's more efficient without testing it out for a while... so we might get less clicks because of that.
Also, if you turned on the HubPages ad program then there will be more ads on the page which would mean less click throughs since it also displays less Google Ads that normal.
And lastly, people might have noticed that HubPages is a low quality site by Google's terms and that the traffic was falling so either they blocked their ads from showing up here (and we now only get the scrape the bottom for the crappy ads) or Google themselves only displays select ads on this domain.
BUT I have had a couple days where I get a few clicks that bring in a dollar or so each. But there have been too many days where I only get a handful of cents for a day.. in fact my click through rate this month is .58% when last month it was 1.42%.... and today I got a click, on some random site because it's not coming up as HubPages, but yet I didn't get paid for it?