First time growing

I don't know if your 1.5 weeks is from first wetting the seed or from when it broke ground but it looks good and healthy. Growth is slow at first so don't freak out. It is not unusual for the roots to be 3-4 times as long as the plant above ground. Your little sprout is focusing on a good foundation and should start picking up speed in a week or so. Always Ph your water! I don't use R.O. as it lacks needed minerals so if you stick with R.O. you may need to add some nutrients back to the water. I don't go by lamp height and instead pay attention to the light level at the plant.