Something is obviously wrong. Could be diet, could be they are depleted of copper or some other trace mineral or vitamin, could be boredom, or about any thing else imagineable.
What does this stuff weigh per gallon? LOOMIX weighs 10.8 pounds/gallon, so eating 4 gallons of LOOMIX/day is practically impossible. I have had cattle eat 10 pounds/day of LOOMIX, but for only a day. Found out the next day they had had no mineral for the prior 6 months....put out a bag of mineral and the consumption dropped to 6 pounds the next day, put out another 50 pounds of mineral and it dropped to 2 pounds the next day, and from there it was easy to regulate them.
First...have all your feed tested, and test your water as well. Then, have somebody who knows what they are doing run some rations for you using the results of your feed test. I would personally shut them off from the liquid and just put out some damn good mineral for them until you have a handle on this. The mineral consumption may tell you what you need to know.
Is there a chance they could be using this as an alternative to water??? I have had cows sucking down 4 pounds/day of pure bitter LOOMIX because the producer didn't know his electric waterer as shorted out and every time they went to drink they got the sh*t shocked out of them.
Time spent observing them may give you your answer as to what the problem is.