Rick:
This explanation sounds good. However, I do not know whether there was some
UV filter in front of the flash or not.
I used UVA-light tubes, exactly those used in solariums, too. I mixed two
UVA tubes with two warm white tubes and one cold white tube and I had very
could results in leaf-colours.
Some Pings (agnata and caudata) however, were a little bit sensitive and
produced ill-shaped leaves sometimes, when being to close to the tubes.
Greetings
Michael