Sounds like Leprechaun is right. Get those lights closer to the plants. You should be able to hold the back of your hand at the canopy of the plants and your hand feel comfortable. If your hand feels too hot after 30 to 45 seconds raise the light another 1 inch and re-test. The yellowing leaf tips on the older growth is most likely due to the plant using its nutrients. The other thing it could be is Nutrient Burn. Be sure not feed nutes for the first 2 - 4 weeks after seedling has popped up. Depending on the soil you are using, you may not need supplemental nutes at all. FoxFarm Ocean Forest has all the nutes you need for the entire life cycle as long as you transplant every 4 - 6 weeks.

Hope this helps a little!