No vertical growth on new plants

I just started growing 4 new plants. They are 6-9 days since they sprouted and are very short. The leaves are developing, although they are only on their 2nds set of serrated leaves. The tallest which also has the biggest leaves is only about 2 inches tall. The shortest with the smallest leaves is 1 inch. Seems they sprouted and grew a bit and then stopped moving up. I have them under a 90w UFO. It is about 6 inches (?) above. Is this too close? Is this nothing to worry about? Is this a good thing? They are in solo cups and the top of the soil dries out after a couple hours but the bottom is always heavy with water. I tend to just mist them a few times a day and water them every other day or so with a few ounces of water. I also just started adding succunat. No nutes yet.

6" is definitely not too close for an LED light. Your plants could probably be an inch away and not get burned. I haven't ever grown in solo cups or used an LED light so I can't give any other advice, sorry.

I moved them closer but then added 2 cfl's to my grow box and had to move them a bit further away again. Probably back to about 6 inches from the LED again and 3-4 inches from the CFL's. Best I could do with the box I have. The CFL's are directly below the outer part of the UFO. They are daylight 6500k so they aren't too hot. When I flower I'm going to switch them to warm light CFL's.

If you are growing from seed it will take a lot longer for plants to reach maturity enough to switch them to flower - between 6 weeks to 3 months of vegging, vs the 3-4 weeks of vegging when growing clones. Don't confuse the speed at which you see clones or cuttings grow to that of seedlings. Cuttings are off cuts of plants that are fully adult already.