I would suggest taking it to a gunsmith. Saying DA is weak doesn't give much info on what might actually be wrong, if indeed anything is. The end goal is to have the gun index correctly and lock up tightly on firing, but the ways one determines this isn't a simple answer. If you're curious, ask your gunsmith to talk you through what he's looking at - for anyone with some skill in gunsmithing it's intuitive, so they'll be able to point out what they're looking for and how they test for it. This way you'll have an understanding of what to look for in the future.
Plus, just getting them to look at it will probably be cheap or free.