Your soil mix looks very dry to me in your photos. I don;t use any special water on any of my aroids or other tropical plants out in the greenhouse. Its just well water, straight from the Florida Aquifer and very high in dissolved iron and the minerals because it passes through many layers of limestone. They don;t seem to care.
The only plants I use reverse osmosis water on are my terrarium plants, mainly because a select few that come from the cloud forest require pure water, and also because it cuts down on spots forming on the leaves and glass in the terrariums
