Seems like there was a change in the last couple days that effected the difficulty. The difficulty for my miners has been much higher than normal. Anyone else seeing this? My S4's in the past typically had a difficulty of 4096 (even though I have d=2048). But now they are at 8192. And my 1TH/s miners went from 2048 to 4096. Pretty much doubled, for all miners. I know that overall the payout is the same, but it made the graphs very "jumpy" and at first I thought there was a problem. Actually, as I look again while typing this, the reject rate has increased, starting 1.5-2 days ago. I'm just wondering if there is an issue on my end.
I've got a few S1's and several S3's on westhash and have seen the same increase in difficulty you have, but at lower numbers. I used to see sub-1000 difficulty but all of them are now 1024 or 2048, which is not normal.
So I'd guess that no, it's not an issue on your end of the connection.