It would be nice if they FAQ'd it but the rule says only the unit with the drugs is affected by them. Since the archon is an IC he's a unit of one.
I think the idea is that units with combat drugs are under the influence before the game begins, not that they're handing out the drugs to units they join. And since the effects are in place for the whole game it doesn't make sense if the units he joins gain and lose the effects as he joins/leaves them.
Tyranids, Hive Fleet Chimera (7,000 points)
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