I had an issue with root rot on both my Thai constellation, and my black velvet alocasia. For my black velvet I did a peroxide, water, and a tiny bit of neem oil soak on the roots that were left. I threw out the old soil, down sized the pot. For the Thai I have constantly had issues with this plant, either bugs or now root rot. I have went ahead and took some advice from a previous post. Trimmed up the roots soaked in peroxide and water mix. Dried her out for a few minutes and downsized her pot. Now added little small rocks and pebbles to her soil mix to hopefully open up the soil for more air flow. I really appreciate everyone’s help on my previous post. We will see what my lovely plants have in store