My husband was having vivid dreams and hallucinations, but now they have stopped. What is going on?

I guess be grateful that they've stopped if they were bothersome to your husband, but you are best to ask his doctor these questions.
And if your husband has already been diagnosed with dementia, then you should already know that things never stay the same.

In your last post to us, you asked why your husband was having vivid dreams and hallucinations. Now you're asking why they've stopped. We cannot possibly replace a proper medical diagnosis as a forum of lay people. Please have the man seen by his PCP as a starting point to get him diagnosed.

Good luck.