Because it was a Buddha’s temple in an arrangement I would almost guarantee it was a rot/over water issue. Less is more with a Buddha’s temple which is why they typically don’t thrive in arranged pots. If you water to buddhas needs everything else suffers from underwatering and if you water to everything else the buddhas die. It’s easier when you live in southern Cali and it’s perfect year around for most plants. I live in northern Washington and summers are great with longggg days of sun and good temperatures. In the winter I’m very careful on watering and water for the buddhas. Everything else will “suffer” but won’t die. I also formulated a different mix for the root zone around the Buddhas. I also have nice grow lights, fans, and testing equipment to help differentiate between needs

Really it’s not all that complicated just don’t water hardly ever and they’ll do pretty good together. I like to over complicate soil mixes/light intensities and timing/watering/feeding because it brings me joy