Although 30 is a bit young for the development of significant under eye hollows, it certainly occurs, to some degree or another, often enough in my experience not to raise an eyebrow. Fortunately, treatment these days is pretty easy via the use of fillers, such as Belotero Balance. A natural, hyaluronic acid-based filler, Belotero flows easily and possesses little to no tendency to give rise to the unwanted, bluish Tyndall Effect when injected superficially into the delicate tissues under the eyes, making it my filler of choice for this purpose in my Upper East Side Manhattan office. (In my Israel satellite facility, where a far greater number of regulatory agency approved fillers are available, I typically opt for Teosyal Redensity II). In experienced hands, treating undereye hollows should take no more than five minutes under each eye and typically evokes an immediate "Wow!" response following treatment. Treating this region should not be left to the hands of inexperienced injectors trained only to treat simple smile lines with ordinary Restylane. Make sure to consult with a board certified aesthetic physician and of course ask to see his/her before and after photos before proceeding. Best of luck.
This would be best addressed with under eye fillers. Do you have any cheek filler? You have unusually full low cheeks which are consistent with certain filler treatments. This area tends to have long term changes that are not related to body weight so if you regain weight, it is unlikely this area will snap back. The key is finding a highly experienced injector who treats this area. I have many patients who fly from Texas to see me so I know finding the right injector is challenging.
Your issue is more likely from the weight loss rather than the aging process. Unfortunately, if you were to gain weight back, one cannot direct that fat to go to a certain area. I think fillers in your tear trough woudl correct the problem.
Thank you for providing the photographs. You seem to have a good complexion, little in the way of eyelid bags or other deep facial lines. Based on the photos you would be an ideal candidate for tear trough filler injections. These areas are difficult to treat well, so it is essential that you ensure that you seek treatment from someone with a lot of experience in managing this area of the face.These aesthetic issues are very common and are not due to sinusitis. Tear troughs are not really a sign of 'premature' ageing as they often appear in the 20s and 30s as a normal part of facial development, and can definitely be associated with significant weight loss. Best of luck with your treatment.