Lots of possibilities -- too close to the lights, too high of soluble salts level in the soil, too dry, humidity too low.

Are they dead tissue, or just pigmentation spots on a variety with pigmentation?

Temp too high -- after it germinates, it grows best at something like 55 to 60 degrees.

Denninmi, I thank you for taking the time to respond as do my 4 guinea pigs and 2 rabbits who are patiently waiting on this crop:)

I am using cool white bulbs set about an inch above the tops. They are on for 16 hours and off for 8.
I don't know about soluble salts..
Possible that they are not wet enough after reading more about lettuce water requirments.. I'll be a bit more free with the watering.
Humidity could be a problem as well. I don't run the heat much in my house in winter so it's not overly dry inside. But maybe too dry for them. Do you see any problem with me misting the leaves to add humidity? Or is this likely to add to my problem?

It does not appear to be dead tissue but it's hard to tell the spots are about "pinhead" sized.

I keep the temp in my house at about 65 degrees, so I don't think that it's too hot..

I wondered if this was an air circulation problem, so I thinned them out to one plant per cell.

I have a flat of Romaine growing next to these Bibb and I have not noticed any spots on these. Not sure what this means but interesting..