Funny, i also had a major melt on my end. Lost almost half of my crypt growth. I planted mine and let the leaves melt off into the tank. With in the next couple of days i was seeing massive melting. Its only affected my crypts.
I've been looking into allelophathy as a possibility.
I did a massive water change and so far the melt off has stoped. Im also seeing new growth.
Congrats on the success so far. I hope it keeps up.