Well, what were your temps with the 60W and now with the plant light? Measure the temperature directly under the strongest beam of light. That's the real question, but you'll have to measure, we really can't guess.
I can't say much about the black light since I've never used them and I'm not 100% sure that it wouldn't bother the geckos as the packaging indicates. I would prefer that you use a bulb intended for reptiles, the plant light you are speaking of is a full spectrum bulb, but it is designed to balance the UV (I don't know if it is A or B or both) and visible spectrum for the best growth of plants and I've used them a lot for that purpose. A normal household bulb doesn't have any UV and is ok, but not great as an option for geckos. You should really look into a reptile bulb with has visible spectrum and UVB. In my opinion and experience, when you include UVB you will find that the geckos are more active and have greater appetites. They can be found at any pet store and are no more expensive than the plant bulb. So, I guess what I am saying is best is a reptile bulb, second would be a normal bulb, but I wouldn't use the plant bulb unless you know what it is putting out.
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0.1 Albino Leo Gecko
0.1 Crested Gecko
1.0 Dear Boyfriend
Departed: Harvey and Spock