Yes the explorer is sometime wrong because of the way it deal with orphan block.  The pool not really went negative, it's just that these 28k newly created coins has been reject by the other nodes.  At this low of a difficulty we was (all POW miners) creating a lot of block really fast and because they were almost all replaced by POS block the difficulty had a hard time to adjust correctly.

And for the title,..... I would like it to be removed too, but we have no control on the title