Yellowing plants from tip with a slight curl!

Hi
I am growing indoors and all was fine until the plant started to bud then all of a sudden they started to turn yellow at the tips, moving inward until the whole leaf was yellow. The buds stopped growing. I lowered my PH to 5.5 ,and PPM to 600. The temperature in the enclosure fluxuates between 76-86 degrees. I am feeding it with aqua grow and aqua bloom. Is there a solution?
They are being fed 3 times a day for 15minutes on a timer. The light is 1000 watts. it is 12 inches away from the top of the plant.
Is there a solution or should I move on to the next batch? Technically they are supposed to be harvested on Friday, but the buds are really small. Will they stil grow?

might be overwatering.... damn thats one spindly little fucker isnt it?

How far away are your lights? Those look stretched, it could be that they're not getting enough light to support growth.

They are being fed 3 times a day for 15 minutes on a timer. The light is 1000 watts. it is 12 inches away from the top of the plant.
Is there a solution or should I move on to the next batch? Technically they are supposed to be harvested on Friday, but the buds are really small. Will they still grow?

is that a mh or hps bulb? i cant tell from the pic, they are very stretched, and the temp should be 70 at best, and whats the age of the plant?

I just had some plants that looked like that and I would say that it is a combination of too much heat and over-watering. It could just be the heat but since I changed two things when I had the problem, I can't say for sure. But at a minimum, the temp should be kept around 72 degrees. If the room is getting into the 80's , it is likely that they don't like the higher temp, resulting in the problem you have.

Thanks everybody for the feedback I've received up to this point...
But I would still like to know an exact light schedule from clone to harvest. Also does the feeding time corrolate with the light schedule and if so what is it?

From seed/clone through veg stage, I have the lights on 18 hours and off for 6. I have seen that you should have the lights on for at least 16-18 hours but I go with the latter. For flowering, I set the lights to 12/12. My propagation kit says to have the clippings (starting clones) on for 24 hours but I stick to the 18/6. Once you have harvested, you don't want any light, because light will degrade the THC as you dry/cure. Hope this helps