You'll probably find the reason for the dropping hashrate is because the front-end has been down for a couple of days and miners don't like to leave their machines hashing when they can't see how much, or if, they are getting paid for their hashpower.
There was no down time. Can you elabore what kind of down time you are talking about?
The total SHA256 hashpower hasn't decreased, but moved to WestHash market. You might check it out.