bartles Gazanias are low-water consumers, and I'd bet they have too much water, which can certainly weaken and yellow them. Why don't you hold off on the watering them until the soil is nearly dry (recommended for adult plants) and as purple says, give them plenty of light. Also Google gazanias and water for more information on their cultivation needs. They're great flowers for dry spots.

Purple stems on seedlings are okay. Sometimes the leaves will be purplish too. They will green up as they get older and warmer. I forget what it is, but purple means it's not getting something (either P or K) because it is in a cool environment. Someone will chime in with the science, but it is not a problem at the early stage. Don't try to do anything to correct it. All of my seedlings do that because I start them in the cool basement to keep them growing slowly rather than shooting up and getting leggy. Thick stems and true leaves are an excellent sign. Keep up the good work.

I definitely would not bother potting them up. For fertilizer you can use what you have, as long as it has nitrogen. Other natural fertilizer options include bloodmeal, fish emulsion, manure tea and worm casting tea. When transplanting them out, you'll want to clip off some of the lower leaves and trench them in good soil. Like missingtheobvious said, you'll want to start them in shade and very gradually expose them to direct sunlight. But you'll also want to keep them out of strong wind. Those big leaves are very soft and wind will chew them up, and stems can get crimped at the base seriously compromising the quality of the plant. Below is a link with a diagram on trenching leggy tomato seedlings. Here is a link that might be useful: Trenching Leggy Tomato Seedlings

Hi chlobell, Answers to your questions: "1. Should I cover them and turn the heat mat back on?" No, they don't need either. "2. Our outdoor temperatures are warm now (70-80 degrees). Should I bring them outside for a few hours instead of letting them sit all day under the grow light?" Your temperatures are warm enough that you could start that now. Begin with a couple of hours in the shade then gradually increase the time, moving them into filtered sunlight and finally full sun. "3. Given that it is warm enough to plant outside now, how big do they need to be before I put them in the ground." Most of the time we plant out when the tomatoes are at least 6-8" tall, but that is for tomatoes that are started indoors before it is safe to plant them out. I'd wait until they get at least two sets of true leaves. Now I have a couple of questions for you: What medium do you have them in now? Is it a soilless seed starting medium? It looks pretty wet to me, but I could be wrong. Are there drainage holes in the bottom of that container? If the growing medium is too wet, that could account for the slow growth, particularly if it is also a "heavy" mix. We usually wait until we have true leaves before potting up, but that medium may not be the best for growing seedlings, so you might consider transplanting them into a standard growing medium (potting mix, not soil). If you do that, then wait 4-5 days before putting them outside. I hope that helps. Betsy Here is a link that might be useful: Hardening Off and Physiological Changes