Yeah, it's likely the flouros. When I moved my seedlings from starter cells to a new bank of T5s, like 8 weeks ago, I did not understand how strong those lights were. So I put them at 2-3 inches above the seedling tops. Most of my plants went dark purple - ALL of the leaves. I backed off the flouros to about 10" and things got more normal. I eventually figured out that 2-3 " stressed out the plants too much, and the lights then sat at around 6" above the plants, where they did just great, with only occasional minor purpling.
Anyway, oddly, the purple leaves never seemed to affect anything. They didn't turn brown, die, fall off, go green again, or anything else. They just remained healthy looking, but purple, leaves.
Here is a pic that illustrates the whole situation very nicely. The plant on the left, a Thai Hot, went 100 % purple under my T5 setup. About 10-14 days ago, I pulled it out from under the lights and just put it out in the sun. Thus you can see on the plant, lower leaves that are entirely dark purple, followed by a sudden, total change of direction where the new leaves are a healthy dark green. I think my learning point from this odd purple experience is to not panic when it happens because it doesn't seem to mean anything, but also to keep those T5s more like 6 inches off the plants instead of 2.