Exactly the same thing happened to me. I went from 12 points in ERA and WHIP to 4 points in ERA and 5 points in WHIP in two weeks (and from the #1 ranking in the country to #60). I've never seen anything like it. I knew that I'd been on a lucky streak to some degree with my pitchers to this point, but still.
My strategy has been to stay active in looking for guys who will close out the year well, but the key is not to panic. I think your idea about MRs has some merit and if anyone is available jump on them, but mainly you have to "ride the horse that brung ya".
2008: 37th ranked Yahoo PLUS Rotisserie Public team (24 weeks in top 45, 9 weeks as #1)
2006: 18th ranked Yahoo PLUS Rotisserie Public team (17 weeks in top 35)