What does “Too much toothpaste has left the tube” mean? Is it a well-received turn of phrase?

I was drawn to the phrase, “Too much toothpaste has left the tube” appearing in Washington Post’s (January 13) article under the title, “Comey should resign.”

“(FBI Director James B.) Comey was in a difficult situation, boxed in by Clinton partisans and heading an agency that allegedly was expressing distrust of the Obama Justice Department. By all accounts, Comey is a decent man and a straight shooter, and it’s unfortunate that the Clinton scandals landed him in such an untenable position. But too much toothpaste has left the tube. The FBI won’t be thought of as being at its best, and the agency’s investigations and actions won’t be met with complete trust, unless there is a change at the very top.”

I often hear the expression, "You cannnot push toothpaste back into the tube," but I've never heard of “too much toothpaste has left the tube.” Does “toothpaste” here represent unsettled problems or suspicions on the stage? Is it a popular turn of phrase, or simply a writer’s coinage? If it is a well-received expression, how can it be used in other contexts?

It is apparently equivalent to "too much water has flown under the bridge" implying too much happened that can't be undone now (in the context of the question: the situation cannot be rectified under the current leadership).

TFD (idioms):

water under the bridge
A past occurrence, especially something unfortunate, that cannot be undone or rectified:
All that is now just water under the bridge.

American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.