Are you running these cards in 1 rig or 3? What mining software are you running? What are the settings for your cards?
2 rigs actually, on has 2 GPUs. Running cgminer through GUIMiner-scrypt. Maybe I'll update it when the rigs are back up ( rigs are down due to power failure in the area).
Settings (from memory), are close to this:
-g 1 --thread-concurrency 7500 -I 18 -w 256
as someone suggested it in this thread, I also tried adding
--expiry 5 --queue 0 --scan-time 5
Seems to make no difference.
I an running multiple 7xxx cards and my reject rates have always been low on HC.
Must be your config.
That may be possible, but other pools don't report such high reject rates, including middlecoin, give-me-ltc, etc. Most report under 5% rejects.
You probably did not use --no-submit-stale with cgminer... This is why the high reject rates.
Turn that option on and try again.
But that will only mask the rejects, then I'll only see the efective hash-rate at the pool and never figure out why there are so many rejects in the first place!