One of your breast implants has dropped and the other remains in a better-appearing position. At 6 months your tissues have healed (nearly completely) and your internal and visible scars have likely faded and softened as well. Wearing a bra or elastic bandeau will not have a beneficial effect on CHANGING implant position, but may help to MAINTAIN position from further dropping.
Depending on the technique and practices of your surgeon, you can either have a thin, soft, pliable capsule around your implants, or perhaps a thicker, more firm, and less stretchy capsule. The former occurs with careful, precise surgery and control of capillary bleeding, and avoidance of bacterial contamination and resultant biofilm induction at the time of pocket creation, as well as maintaining post-operative limitation of activities that could cause bleeding and a thicker capsule.
A thick, firm capsule that does not stretch or soften over time occurs when the surgeon uses blunt dissection technique, surgical drains (rather than control of bleeding and bruising), and when he or she is, shall we say, less fastidious about bacterial contamination (implants out on the Mayo stand, sitting on cotton surgical towels, being touched by the surgeon's gloved hands--that touched the patient's skin, and being inserted through the incision dragging skin bacteria along with the implant; all leading to biofilm formation and higher rates of capsular contracture).
You may know the cause based on the degree of bruising, swelling, and pain after your surgery, but it is clear that what happened on one breast did NOT happen on the other, and there could be any number of potential causes, some of which can be attributed to the surgeon, some to the patient, and some to random chance.
At this point in time, the correction involves creation of a tighter and higher capsule on the side where the implant "bottomed out." This can usually be corrected with sutures alone, but some degree of over-correction is likely necessary, as well as wearing of continuous bra support for a minimum of 6 weeks after surgery. This operation may need to be repeated, but this is very unusual. Implant crease raising occurs in less than 3-4% of my breast augmentation cases, but I believe implants ALL drop to some degree in most all patients, so I "build in" a certain degree of over-correction initially. This reduces the number of re-operations for bottoming out, and if the implants don't drop quite as much as necessary for the best-looking result, it is a much easier (and successful) re-operation to DROP the implant pocket a bit, rather than raise the pocket and hope it stays there despite gravity, implant weight, and external bra support (and I tend to have patients who like large implants).
You probably do not need Strattice or other ACDs, and these are expensive and don't always last long-term anyway, so I would defer this decision to your operating surgeon, who knows the condition of your tissues. I rarely need it, and even more rarely use it. For an example of a patient with "bottoming out" on one side after vertical lift (elsewhere), click on the link below. Good luck and best wishes!