Answer: In the garden, zinnias need full sun all day long. Unfortunately, it sounds like they are in need of a lot more light than they are receiving. It is difficult to grow good quality transplants at home without a greenhouse or supplemental light. You could use a shop light with one "warm" color bulb and one "cool" color bulb, keeping the leaves within an inch or two of the bulbs. At this point, I think your seedlings may have stretched too far to be salvageable, but you could try pinching off the growing tips and see if that plus additional light helps them grow bushier from now on. There is also still time to try again with new seed.
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