Also, like they said, you could reduce the primers, but do it by 1/2 or 1/4. 0.8x isn't much of a change. However, stay within the concentrations I gave.
If you look at the primer sequence, see a homology of 3' ends, you can show it to the appropriate 'hands' and suggest a modification of + or - or shift a nt. or two.
You could also run out some primers, in PCR buffer in case it causes double strand annealing, to see if they are visible on the gel by themselves (I'm not sure that single stranded couldn't be visible in some conformation).