I don't have enough experience to say this from my own observations, but what I read agrees with what you said: insufficient blue light can sometimes cause elongation.
But that might be caused by either a too-red spectrum, or just plain not enough brightness. I think that adult plants usually need more brightness than seedlings, but others on this thread have MUCH more experience than I do.
>> two 42-watt warm white CFL's. totaling 5400 lumens of light
I have less light than that and my seedlings don't stretch out too much even though I think I have marginal overall brightness. I aim my CFL bulbs to cover 3-4 1020 trays. How much area are your 5400 lumens spread over?
I do think that adding or replacing one or both warm bulbs with daylight or "cool" or "bluish" bulbs would help you.
