First time growing auto flower seeds

They are auto flowering seeds and is this how big they should be at 5 weeks old or am doing something wrong? The tallest plant has yellow spots on the leaves. The other 2 don’t. I’m also first time growing hydroponic

Do you have intake and outtake fans ? Air circulation is imperative
Also check the temp of your room, should be 25 - 27 Celsius. Also your walls should be white to reflect the light.
Yellow spots probably mean your nutrient levels are wrong.