You need to address the reason your very young hatchling already has MBD so soon, or the liquid calcium will do him no good at all. Why do you think he has MBD already? 8-9 weeks old is extremely young to already be showing outward signs of having MBD, even if he's never had any
UVB light or calcium and multivitamin powder supplementing at all since birth. So if I were you, I'd post a photo of your baby, along with photos of his complete setup and lighting, because #1 he may very likely not have MBD, and more importantly #2, if he does have MBD it's most likely due to having an inadequate UVB tube.that is also mounted incorrectly and at an improper distance from his basking spot. Without a proper wavelength and strength UVB tube mounted in his enclosure correctly, his body cannot manufacture vitamin D3, and then he will not be able to absorb any of the liquid calcium or any of the calcium in his food anyway. So unless you get your husbandry straightened out, giving him extra Calcium isn't going to help him, the calcium deficiency he has will continue to get worse.
Please list the brand/model/type (compact, coil, tube, or MVB) of your
UVB light, how old it is, how far away it is in inches from his basking spot, and whether or not it's obstructed by a mesh or glass lid. Then tell us what basking bulb you're using as well as far as it's color and wattage. And what is the Basking Spot temperature, the Hot Side ambient temperature, and the Cool Side ambient temperature inside his enclosure? What type of thermometer are you using to measure the temperatures (stick-on, digital probe, or gun)? If he's not getting proper UVA light, and if his temperature gradient inside his enclosure are not within the correct ranges, this will also effect the proper digestion of his food, which can also cause calcium and vitamin B1 deficiencies, which both cause similar symptoms....And what size is his enclosure? What is his daily diet (what feeder insects and how many per day)? What calcium and multivitamin powders do you use, and how often? If you can post the photos and answer all of these questions, we can help you get your husbandry and diet corrected so that any health issues will stop and possibly reverse any damage already done.