My problem is this: I am due for bulb replacement, but when I change to the new bulbs, 2 ATI Coral Plus, 1 ATI Blue Plus, 1 Korallen Coral Light SuperBlue, they won't start. They will sometimes light for 5 sec, go out, then relight for another 5 sec, before going out again and not relighting, when a bulb is turned a bit in the fixture. The new bulbs are in the same locations (and orientation) as the old ones. If I put the old bulbs back in, they all work fine. What might be going on? Thanks in advance for any help.