4 months post lower blepharoplasty. Any suggestions?

Most common cause of under eye dark circles is hollowness, which may be the case for you too. See an oculoplastic specialist in person. You may benefit from filler injection. See following video and link.

Hi ANT.  Based on the forward facing photo, you appear to be a candidate for Restylane injections.  Although this does not change the color of the skin, it can help with the shadowing.  Take a look at the photos at the link below to see others that have had success with the same concerns you have.  

You most likely had a blepharoplasty with removal of the fat.  This can create a hollowing of the lower lid which you have.  When you are hollow, the lid will cast a shadow on the tear trough and you will look darker there.  Try some HA fillers such as Restylane to add some volume.  This will usually help improve the shadowing and make the skin appear lighter. 

Generally preserving lower eyelid fat by use of the arcus marginalis release surgery is prefered over fat removal for this reason.  You are now hollow in the lower eyelid area after removal of fat.  The best option for this is under eye filler.  I wonder if under eye filler might have bee a better option for you initially as an alternative to surgery.  I do not advise fat grafting to this area as the scaring created by the grafted fat is also very problematic.

It is common to have some darkness under the eyes after lower blepharoplasty. The brow bone is forward compared to the lower eyelids. This will result in some shadowing whenever there is overhead light, resulting in a dark appearance. If the lower eyelids are very puffy, there will be less darkness as the fat causes the lower eyelids to bulge forward resulting in less shadow. When the shadow collects in the line between lower eyelids and cheeks, it produces a "dark circle" as the darkness is concentrated in this area. Removing the puffiness in the lower eyelids can sometimes increase the darkness.Adding filler to the lower eyelids and cheeks will reduce the dark circle by blending the eyelid-cheek junction and allowing the shadow to diffuse over the entire lower eyelid and cheek, instead of collecting in a circle. You have very thin cheeks, so adding volume into the cheeks will also help bring the tissue forward and reduce the shadowing.

it seems as though you have a delineation between your lower eyelid and cheek tissue. Fat grafting of this area would help to solve this problem and the darkness.

Was your surgeon a fat remover or a fat preserver?  Fat preservation or arcus release uses your own fat to fill hollows and is my preferred way to do this procedure.  Fat removal is easier but can leave hollow eyes down the road and a greater tendency to having shadows.  And if you have shadows now, fillers may help and can be tried and if it doesn't, it will be gone in a few months.