qPCR: do both primers have to contain a GC-clamp in order to be effective?
You can have GC-clamps (3' terminal G/C) in both primers; this may overall improve the PCR efficiency. However you should take care not to put too many G/Cs. This may lead to stabilization of primer pairs, leading to formation of primer-dimers. Also see this post: When designing primers how important is the GC clamp?

GC-clamps are not always essential and you should look at other parameters too.