If your volumes were accurate with the estimates from BeerSmith, then you can update the brew house efficiency in your equipment profile to match the efficiency you are observing. Open up the last recipe you brewed and make sure you have filled out the gravity readings and volumes you actually measured in the 'session' tab. On the left hand side of the tab, you will find a calculation of the 'meas efficiency' as compared to the target from your equipment profile. Update the profile with this new measured efficiency and you should be in a better position. Save the equipment profile and update your next recipe using this profile to apply it to your recipe. You will most likely need to adjust your grain bill to get back to your initial targets.
If your efficiency was much better than the original efficiency from the equipment profile you used when you initially brewed the last recipe, you may need to use 'scale recipe' to adjust the bill of ingredients while updating the recipe to the new equipment profile with the updated brew house efficiency.
Just a note: BeerSmith treats all recipes as an archive. When you change something in your equipment profile and save it, the program will NOT update any existing recipes that you have made or brewed previous to that change.