I have a peace Lilly/anthurium plant I’ve had since 2007, it was a gift when my grandfather passed away. It was doing great till about sept it started dying. I think it was the period of heat/humidity. I tried moving the plant to an area with more light (not direct sun), still was dying. I noticed a white mold? On the top of soil, I replaced the top part of soil which didn’t help. I finally cleaned the whole pot and replanted plant in new soil. It still is not coming back to life, I hope there is something I can do to save it. I have a couple of photos I can email you of what it looks like now.
It sounds like you had a mineral buildup on and in the soil which can be mistaken for mold. Repotting was a good idea. Check to make sure that, when you repotted, you didn’t bury the stems any deeper than they were previously…the soil level needs to be exactly were it was before repotting. It is also possible that it is getting overwatered…the soil wants to get fairly dry between watering. If it has a saucer under it, there should never be water left standing in the saucer. When you water, any water that drains into the saucer should be removed after no more than a few minutes. You can send pictures to firstname.lastname@example.org if you wish