GPU has extremely high idle temp

[TheDoctorIsIn]

Today, I started up my computer, did a little bit of web browsing, then immediately went outside to do some landscaping. It took me maybe 30 minutes at most, and when I came back, I decided to turn on MSI Afterburner, as I typically do. It was then when I noticed that my first GPU (SLI GTX 670's) was sitting at about 75°C. What gives? After turning on MSI Afterburner and waiting for a bit, temps are back down to reasonably safe levels (If you count 59°C at idle "safe", that is)

Any tips on how I can keep my temps down? I already have the two fans on each of my cards spinning at 100%, a case fan, AND a regular fan pushing cool air towards the chassis. Any help is greatly appreciated.

 

[neon neophyte]

blow the dust out with compressed air. if that doesnt work you may have to remount the heatsink with fresh thermal paste.

 

[TheDoctorIsIn]

blow the dust out with compressed air. if that doesnt work you may have to remount the heatsink with fresh thermal paste.

There is no dust, as I had taken them out a few days ago for routine maintenance. (checked fans were working correctly, extensive dusting; basic stuff) I do have some thermal paste though, so I will try that when I can and get back to you.