First Grow Leaf tips curling and dying

Hey this is my first was wondering if you all could give me some help. I'm using 3 gallon pots, happy frog, 400w magnetic switchable ballast with a mh bulb, I'm using heavy 16 nutes just grow a & b for right now adding additives next watering, and the plants are about 5 weeks old. 4 days ago I noticed the leaf tips curling on some branches and these pictures are from yesterday. Any help you all could give would be much appreciated this is my first go round at this.

i dont have a lot of exp. but looks like to me too much water to me or a nute problem

They look pretty good to me. Back off the nutes a couple waterings and make sure your soil dries out real good, like bone dry before you water again. Don't think yoou got a problem.

Thanks for the advice I haven't added a full strength nutrient watering yet do you think that I should do that at all?

I use Heavy 16 and always at half strength. I do use it for hydro, but same principles apply. Don't know what you're working with but if you can make sure your water is ph'd correctly and record the ppms/ph for every feeding. The leaves look fairly dark on the plants, probably overfed a bit. I would just water with plain water for a couple rounds. They look fine though I don't think you have anything to worry about.

The yellowing is staring to spread to the tops of some newer growth and these leaves are curling up making a c like shape any ideas? I watered with plain filtered ph water i dont have an ro system I use a brita filter.

Still using just heavy 16 a&b or have you added anything else? Sounds and looks possibly like a potassium deficiency. More pictures would help. I came across this a couple days here on RIU though it might help. Nutrient deficiencies:http://www.mediafire.com/view/?698qtya72u9w03a