Hello,

The 15 watt light may be able to support plant life, but the growth on the clones will be minimal, they may stretch a bit, and being under such a low level of light, the bigger leaves on the clones may yellow up and die off.

Is there any other fluoros that you can get under the lights. Can you run to Home Depot and purchase a shop light?

I think that it is a bit long to try and keep the clones under the fluoro without the addition of some more light.

Take care

Peace