I have 3 canna rhizomes planted in pots under my MH light, near the edge of the area. Light output is about 1200 FC. Is that enough for that type of plant??
1,200 FC should be enough to start them off. Are they going outside in the summer? I don't think that will be bright enough light to grow them on or get them to flower.
Unless you have tons of room, it's too early to be starting cannas indoors when they won't be able to go outside for a couple of months.