I have been having upvote, resteem, post, and comment issues ALL DAY. It does seem like there is an error in the code that doesn't allow certain function or momentarily has an issue accessing any database or script calls if the load avg / traffic is high. It may not have anything to do with a DDoS attack. They may need to either up resources for users or find a different api, I don't know just my 2 cents that aren't worth much! PS I was able to upvote and resteem this after several attempts!