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I'm not sure if there's a fitting for adapting a smaller conduit diameter to a larger one. Looks like reducer bushings are more common anyway. Based on the parts I've seen, maybe there would have to be a box or conduit body in between to facilitate up sizing with common parts, or am I missing something? Just wondering how interchangable this stuff is... perhaps a reducer would fit in a coupler, and another reducer into that, but the size through the coupler might be reduced (or stepped down on one end to step up on the other).

New house, seller had some electrical issues to resolve with the detached garage after closing. These lights worked previously after their repair for a week or so, but the other night after use, and then five minutes later, all three only glow purple on the ends. This occurred after a heavy ran, the power runs from the house in conduit, I do not see any evidence of recently disturbed earth. Each is wired from a single junction box into three separate switches for each light. I tried testing with a new bulb, same issue.

The main power wire runs into the junction, two runs out, one to the two far right lights, and the second into the light on the right. Hot runs into each switch, I assume they're wired parallel. I don't think one bad ballast or switch would cause all the others to not light? I did some electrical helper work in my early days but long since forgot the more advanced wiring methods.