Discus Fish - wont eat - poss mouth problem

Question
We have purchased 2 Discus fish recently.  In 40 (45?) gallon tank with 2 small angels, 3 Head & Tail Lights, a small plecostamus,  and 3 small glofish.  They were very skittish when we got them home.  They startled when someone came near the tank and once in while, darted so fast, we were worried that they might smash into the glass.  

Is is possible that they could smash into the glass so hard as to break the bottom jaw?  One of the fish will no longer eat and it looks like it cannot open its bottom jaw enough to take in food.  What should we do?

Answer
Hi Jane,
Discus fish are very hard to keep, and should be alone in your 40 gallon tank.  Their water must be soft, and acidic.  Water conditions for discus fish is very very important.  The slightest change in there water conditions will make them stop eating, and it is very hard to make them eat again.  They do not do well especially in a 40 gallon tank with other fish.  One Angel fish needs 10 gallons, and more.  Discus Fish need 20 gallons or more for one fish.  They scare easy, and Angel Fish are Devils, and once their territory is made, no Discus fish is a match for them.  Their water should be 82 degrees, and higher is best when they are kept alone.
Check your water to make sure there is no ammonia, or nitrates.  PH should be 6.5.  This is a "must."  
They should have driftwood and many plants, silk or real in their tank.  
What you must do now, and hope for the best is either bring your other fish back to the Pet Store for a credit, or bring your Discus fish back.  They will stop eating, and will live in fear if you try to keep them in with your other fish.  They just let themselves die if the conditions aren't right.  I kid you not!  I have bred these fish, and made quite a few mistakes in the beginning.  I learned the hard way.  
Check your water, make sure that the chemistry is right for your Discus Fish.  They are beautiful fish, but need lots of care.
I don't think he broke his jaw, but is probably stunned, and afraid.
It is always a worry when a Discus stops eating, as he could stop, and never eat again.
Hope this helps
Lynda