Do not think the ammonia is coming from the salt I use which is Red Sea since new salt water and tank water reads zero ammoniaStrange. And I'm skeptical it was ammonia. How much ammonia was there? How big of a water change? new salt water generally has some ammonia from the salt.
If there is ammonia in the effluent, that's a sign that the DI was inadequate. Ammonia is among the first things to be released when a di depletes. My RO/DI removes ammonia just fine until the di depletes.