No way! Don't worry be happy.
There's no way a Japanese waterstone or any waterstone for that matter, is going to ruin a DMT 325 stone. Those stones are used to sharpen tungsten carbide tools and tungsten carbide is almost as hard as the diamonds. Using diamonds on carbide is standard practice in any machine shop. I have a couple of double ended diamond wheeled grinders and they are what I use to sharpen drill bits, end mills, etc.
The DMTs do have a break in period after which they hone better than when they are fresh out of the box. This is due to the manufacturing process which electroplates the diamonds in place on the steel forming a type of setting (just like the setting for a ring except all around the diamond particle) which "grows" up from the steel around the diamonds. The break in period removes the nickel from the tops of any diamonds that were coated during the electroplating exposing fresh, sharp diamond.
Don't worry, you and your stone are just fine! : )