Ok, here's the issue. We're installing new 4 lite t5 fixtures with a one lamp em ballast and also installing 1 lite t5 em only fixtures, 277 volt. We're having an issue with the em bulb burning purple after being on for less than 10 minutes after power is dropped. Doesn't happen on every fixture. Been going back and forth with manufacture (coronet) they are having us try different fixes. There's 2 purple wires that they want tied together and we still have same problem after doing so. We've swapped bulbs with bulbs that have been running for over 2 weeks. We've also changed the em ballast and still have the same problem. Anyone come across this before.