Crypt meltdown

I bought 3 beautiful very large, potted crypt wendtii.  After one week in
my tank, they were still looking great.  After the one week, I did a water
change, about 20%, and a couple of days later, I had massive melt down
occurring.  Was the meltdown due to the water change, or would it normally
take a little over a week for the crypt to begin melt down after  something
happens that it doesn't like?  My CO2 reactor took about 15 minutes to get
the pH from the newly changed water down to the pH of the tank.  The pH may
have risen point four higher during that short time frame.  Would that be
enough to send the crypts into meltdown?  Any suggestions?    
"Candle?  What candle?  I don't see any candle, it's too damn dark in here!"