Phals Under T12 Lights - How Much?

[angeleyedcat]

Hello Last spring and summer I grew various gesneriads from seed under 2 shop lights, each has 2 T12 40 watt fluorescent bulbs, they are hanging right next to each other and the gesneriads did well with them about 5 or 6 inches from the tops of the plants. These plants have since been moved elsewhere in the house for the winter.

I have about a dozen phals that I bought a year ago cheap on clearance shelves at box stores. They spent this last summer outside and most are doing fine, still small but there are some good roots on all.

I have put the phals under these two shop lights. Right now both shop lights are about 12 inches from the top of the phals and on for 11 hours a day (just a guess on my part to do it this way) The phals are a medium green right now but they've only been under the lights for 2 weeks so I'm not sure if the current color is just because they were outside. There is no additional light in the room (window is covered for privacy) and it averages 70 - 75 degrees in winter, 50 - 60 percent natural humidity.

Since I do not own a light meter, not possible right now, can anyone please give me a general guideline as to how close to these lights they should be and recommend how many hours they should be on? Also, do I possibly only need one shop light with phals and is this overkill? I kept them both up because it was simpler

Thank you!