Nirvana Aurora Indica 1st Week Flower "Yellow Leaf Tips"

So I've got 2 aurora indica from seed, I vegged for about 3 weeks or less in 18/6 400watt MH. This problems actually occured just before flowering. All the new fan leaf tips were turning yellow and now its progressing and slowly spreading to the side branches/shutes. The other plant is fine. Sorry about the bad pic but when I get home I'll take it out of the closet for better shots.... I'm using pro-mix for my growing medium, 400watt HPS for flower, 2part grow and bloom liquid formula, monster bloom(haven't used yet), and Root excelurator. I mix half tap water and half britta filter it seemed to work fine last time. But if anyone could help me out I'd apreciate it, I can't diagnose the problem without a ph meter. Thanks again!

Looks to me like nute burn. Start off the little ones 1/4 strength, then work your way up as they mature. I had to learn the hard way.

It could possibly be nute burn but I'm not sure how, I've always fed at half strength and the other plant is fine and in a smaller bucket...I'm gona take better pics soon but for now this is the only one I have. Any suggestions? I'm hoping this doesn't continu to get worse

Hows your ventalation? Also, different strains will handle nutes and strength differently. You also have to watch for sodium/salt build up. If it was me, I would flush, water with 1/4 nutes for the one, and leave the one that can handle 1/2 strength the same. Other than that, they look very healthy and appear to be doing fine.

Plants looking nice! This website might help a little.http://www.weedfarmer.com/cannabis/tables_guide.php
I am also growing a Aurora Indica Strain, when did you put your plant into flowering how many weeks along and was it seed or clone?

My ventelation should be fine its a small but tall walk in closet, I air them out daily and always have the door open a crack with a tall oscilating fan. I've been told aurora indica can take stress and is a hardy strain that could handle nutes well. I guess it all comes down to seed genetics cause one is bigger and slightly different then the other