I know this is probably going to sound terribly inexact, but if you put your hand over the plants can you see a faint shadow? if you do, it's probably ok. I know a lot of people feel 4 lamp fixtures produce too much light, and a lot prefer to use only 2 fixtures. Unless you're in a hurry, take your time and try out different heights. I'd start off at 10 or 12 inches, and see how the plants look after a few weeks. If they are reaching up, move the lights closer or leave them on longer. A lot of times things can give meters bad or incorrect readings, trial and error are probably better bets here.

Keep us posted.

Chris

How often do you feed them?

Feed them every time with 1/4 strength of Jack's. Sound OK?

Another point to consider is the amount of time your lights are on. Violets adapt to less light if the lights are on longer. I don't understand all aspects of light gardening as my experience has been almost entirely with t12 grow lite bulbs. I now have a 24" fixture with a two bulb t8 grow lite. The tops of my plants are 8" to 9" below the lights. . . and these aren't violets. I found the light too intense for them & only keep a couple at the very end of the stand. Perhaps when the bulbs are older I can use them for the AV's.

I think finding what is right for your plants will just take experimenting like Chris mentioned. A final thought. . . if your plants are reaching at all, they could also be trying to protect the crown from too much light. Confusing, right?

Let us know how it goes. Terri