According to the Times, the reports were embarrassing for the Pentagon because, in five of the six incidents in which troops were wounded by chemical agents, the munitions appeared to have been "designed in the US, manufactured in Europe and filled in chemical agent production lines built in Iraq by Western companies".
Where were they found? Next to the plants set up by Western companies that filled them in Iraq, of course. Who has control of those plants now? Why, ISIS of course. Don't worry, though, the people who thought it was better we didn't know about these things are assuring us that all those weapons were hurriedly destroyed.