Nick,
We've got a 02 Journey and most likely have the same three fluorescent light fixtures. When I had a similar problem I looked at the ballast on the light fixture.
If you remove the cover plate from the light, you'll see a long narrow printed circuit board with a transformer and several other components mounted on it. That pc board is the ballast which creates the high voltage necessary to light the fluorescent tubes. Take a careful look at the components on the ballast looking for damage. I'm suspecting you'll see a silver capacitor that has leaked it's electrolytic.
The ballasts run very warm and the capacitor used by Thinlite does not last indefinitely when subjected to heat. The capacitor is a wound foil electrolytic and will sometimes rupture indicated by a brownish liquid stain near the ends of the capacitor.
So far, I've had to replace capacitors on 2 of the 3 lights. If you do have this condition, you can just replace the capacitor rather than the entire ballast or fixture.
Below is a picture of the replacement capacitor I've used. The old one will look similiar but is silver.
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Joe & Shelly, Justin, Tyler, Alyssa | Butler PA
2008 Tiffin Allegro Bus 43QRP|Cummins 425|Honda CRV