Hmm.... You shoudn't have actually build a "wall". A good solution would be to just to put a wood frame beetween the two lamps. You can take garbage bags(Black garbage bags are preferable, of course) and staple them on the frame to prevent light from interfering with each of the both side's plants. If you notice this is not enough, consider getting more opaque material that will not let light shed through. Watch out for the stapling part though, make sure you don't rip up the garbage bag or pull on it too hard.

Be sure to watch out for any exterior light that might interfere with the plants(E.G. you turn on the light to get to the closet). You should block as much external light so that the growing/flowering stage isn't hindered. Even a bit of light can hurt.

Cheers with your growing buddy.!

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