You know, I feel like - especially over the past year - I'm seeing more and more posts about issues with Atomizer-type diffusers, both inline and in-tank. From cracking compression nuts to a necessity of more-and-more frequent cleanings (each time requiring a new dialing-in of the needle valve), to clogs from bubble counter fluid (do yourself a favor and just use water!) to complete breaks, to your basic leaks. When they work, they work great! I just don't have much faith in their durability over time.
I've used several (all in-tank), and haven't had any malfunctions, though I've experienced the need for regular cleaning ...which I found obnoxious. My guess is that the issues are a combination of the materials involved (plastic and ceramic, attached with glue), and the relatively high pressure required to use them. It's also possible that the quality of manufacture from factory to factory is an issue, but I've never read anything definitive about this, regardless of the number of people who come to the defense of the Atomizers.
One other issue is that splitting CO2 between 2 or more tanks, all using Atomics, can be difficult or even impossible, depending on the cracking pressure of the individual ceramic pieces. In this case I would definitely recommend using reactors.
However, I didn't answer your question (sorry!). I would suggest you take a pic and point out exactly where it's leaking, ideally during a leak test with soapy water. It's possible it's an easy fix, but my gut reaction is to suggest you get rid of it and build yourself a simple reactor. It'll cost you maybe $30. $40 if you stumble a bit before you figure out exactly how you want to build it. My feeling is it's unlikely you'd ever try an Atomizer again.