Yesterday my 25GH/s Miner from Butterfly that mined at about 26,5 GH/s went down to about 21 GH/s, now i saw with bfgminer that 2 chips aren't working anymore. Any Hints on that?

Bye
Michael

 [2014-02-01 14:48:34] BFL0 51.0C | 5s:21.50 avg:17.49 u:18.56 Gh/s | A:13 R:0+0(none) HW:2/.34%
 [2014-02-01 14:48:34] BFL0a 51.0C | 5s: 3.32 avg: 2.70 u: 2.86 Gh/s | A:1 R:0+0(none) HW:0/none
 [2014-02-01 14:48:34] BFL0b 51.0C | 5s: 3.60 avg: 3.04 u: 3.26 Gh/s | A:1 R:0+0(none) HW:0/none
 [2014-02-01 14:48:34] BFL0c 51.0C | 5s: 3.48 avg: 2.85 u: 3.07 Gh/s | A:5 R:0+0(none) HW:1/1.0%
 [2014-02-01 14:48:34] BFL0d 51.0C | 5s: 3.73 avg: 3.04 u: 3.39 Gh/s | A:2 R:0+0(none) HW:1/.93%
 [2014-02-01 14:48:34] BFL0e 51.0C | 5s:  0.0 avg:  0.0 u:  0.0  h/s | A:0 R:0+0(none) HW:0/none
 [2014-02-01 14:48:34] BFL0f 51.0C | 5s:  0.0 avg:  0.0 u:  0.0  h/s | A:0 R:0+0(none) HW:0/none
 [2014-02-01 14:48:34] BFL0g 51.0C | 5s: 3.68 avg: 3.01 u: 2.79 Gh/s | A:2 R:0+0(none) HW:0/none
 [2014-02-01 14:48:34] BFL0h 51.0C | 5s: 3.70 avg: 2.98 u: 3.32 Gh/s | A:2 R:0+0(none) HW:0/none