did you test your tank water to know if was low and in need of adding calcium?? Sounds almost like turbo calcium to me. That stuff will sting anything it lands on. I hope you are testing the water using good quality test kits. Calcium, alk. and magnesium have got to be tested to be sure any of those levels are low and in need of using something to raise the numbers. Anything that I add to my tank I do so in a stream from one of my returns or powerheads so it dissipates it throughout the tank or in my sump.
I hope this instability isn't going to cause further harm to the clam. They have got to be in an ultra stable environment. I agree with the need to slow down and read up on what you adding so no harm or damage is caused to the tank inhabitants.