Hello grafiti4u, when you say you water it regularly, how often is that? My Dracaena Marginata is quite drought tolerant. It actually prefers to be on the moderately dry side here. Our area is also extremely dry and our sun is very strong during summer, so it is always in that corner of my dining area, where it never gets too hot. Can't grow it outdoors here during summer, it will just get toast with our extremely poor humidity, so always indoors for mine with a bright light access through our west facing windows.
Also I do my repot if I need to during Spring, not when Fall has come about. The indoor plants naturally slow down too as I observe them, so all the more be careful in watering. They return vigor when mid Spring is here. Give it time to adjust, since you have already done the repot anyways. I hope your media is very well draining. New leaf growth will come from the top eventually. They are a bit temperamental, but will come back nicely again. Drooping leaves tells me it may be reacting to the root disturbance, not drinking properly, but you have already repotted, so give it time to adjust. Feel the soil, stick a skewer in the soil and if it comes out damp, delay watering.
