Is the stem too long on this seedling?

Don't worry at all. Some people will say it's bad to have a stretchy seedling, but its not an issue. At the worst you'll have to support it with a wire or stick. I'm growing 80% sativa blue dreams and they stretched a lot as seedlings. No fan blowing and didn't have to help support the seedlings. They where 100% okay. Check out my diary! But if you want to try and keep your seedlings short, move your light closer to the plant. Use the back of your hand to feel how hot the light is. With leds. You can usually be 8 inches away. But as close as 2 inches if its a weaker led.

Your light distance seems to be what is recommended by other growers and phlizon for seedlings and veg. So, everything is looking good to me. Nothing to stress out about. Some seedlings race towards the light while others take their time. If she starts to droop then you may have to worry about support but for now you’re good. If you want to strengthen your plants naturally you can add silica via foliar spray. This will allow your plant to build strong cell walls which in return gives you fat stalks/stems.

Not worried, it'll be fine, just maybe a little gangly to start. It's generally because you're light isn't close enough, you'll find a sweet spot eventually. Lower it a cple inches and see if it stops stretching for the light so much. Put a little stake in the pot against it so it doesn't fall over and put an oscilating fan going over it on low speed, that'll strengthen the stem. Good luck mate Atb