Is yours a mini or regular? The night blue is actually my lightest rm bag because of the lighter leather--my others are heavier. The minis are lighter than the regular size, but again it depends on the leather. My MAB in Night Blue is Lighter than my chocolate mini b/c of the leather. It depends on the leather...Also keep in mind an LV Speedy is very very light--its canvas and leather has much more weight.
It's going to be heavier since it's leather compared to just coated canvas. There are some different leathers however. Some are lighter then others. Maybe needs taking getting used to it since you've been only using the 30 but you should get used to it in no time!