Is this because SpamHaus/CloudFlare DDoS Incident??
This is normally a notice, not to you, but to the ISP's client, that they have used more than their allotted bandwidth quota -- too many visitors downloading too many resources. It's meant to encourage the client to upgrade their service.
But there are specific reasons for this outcome. If a website operator posts a submission to HN (for example), and if it becomes popular, this might produce a spike in activity that could easily exceed the daily/weekly/whatever bandwidth limit.
> Is this because SpamHaus/CloudFlare DDoS Incident??
Possibly, but in most cases unlikely. It's more likely the result of too many visitors / too much traffic for the subscriber's service class.