The plants palisade layer with the clorafill (sp) layer are on the top of the leaf.
I would be willing to bet that the time spent in the grow chamber/room raised the co2 levels , and that helped the plants grow.
The exception could be the fan leaves were fanning the plants and exposed there tops to the light.
As you might want to know if reflection was 100% silver deposited vaccume coating you would get some power past the plants and reflected to the top.
I suggest you spend a 400-600 $ and buy a good photometer to check the actual light output I'll take a big guess at 1-2 % net reflective value.
Note its not done by NASA ,RSS for the same reason. But they only have a budet of $ 10,000 per at lift off.
Just paint everything in the room/space flat white to maximize you efforts. :wtf:
Now think of how many grower put mylar on the floors :smokin: