Dark Areas Between Veneers

There is nothing that can happen to veneers in two weeks. The dark lines might be stain from coffee? The darkness along the edge could be loss of cement behind the veneer but its rare so soon after placement. Go back to your dentist with these concerns.

It's hard to say without seeing you, however it sounds like you may have what we call "microleakage."  This happens if there was contamination during the placement of the veneers.  When there is microleakage, a dark gray line begins to appear at the gumline of the restoration and possibly inbetween the teeth.  If your gums were unhealthy at the time of seating the veneers, and your dentist could not get the bleeding and moisture to cease, this could have created an environment for this type of problem.  Consult with your dentist to see what steps to take.

It is important to have veneers done by an experienced dentist, as many dentists are unfamiliar with proper veneer placement.

Without seeing what KIND of discoloration you see, I can only suggest a list of possibilities.

If during placement moisture was not controlled, blood or saliva could have gotten trapped during the bonding process.  If the preps were aggressive (removing a lot of tooth structure) the nerves could have been damaged and bled underneath the veneers (not common).  If the veneers have edges NEAR the area between teeth and not hidden, the natural tooth structure can discolor (while the porcelain stays white) creating a halo look.

There are many reasons, but most likely you are experiencing a moisture control issue during placement.  Minor issues can be repaired and sometimes a veneer must be replaced.