Hi,
I don't know if anyone else has had a problem with this but my nappies had the elastic fail and after talking to the supplier it would appear that using calgon can degrade the elastic.
My nappies are Littlelambs, I don't know if it is a problem with other brands too, but they are now going to start advising customers against using calgon because of this problem. The advice is to use white vinegar instead.
I just thought I would pass this on in the hope that I can save someone else the problem.