Help the og please!

I've got three OG plants growing Canna coco in a mylar tent (6'x3'x2') with a 250 W HPS light (and reflector) , and I just added nutrients to our water. I added 3 ml of coco A/B to 5 liters of water. Plants are running on a 18:6 cycle and being watered every 12 hours.
We had the plants lifted about 1' to 1.5' from the light, we just recently dropped them down to about 3'. I've grown from seed, keeping our waters PH around 6.0.
We had humidity problems but I purchased a humidifier which brought our humidity to around 40%. For ventilation we have 2 6 ml computer fans and larger consumer fan blowing into the tent.
The leaves of the plants are curling and yellowing on the bottom leaves of one of the plants, please help!

people are going to ask for pics mate it could be numerous things so take some pics and get them up.. peace

sounds to me that you've got that light a lil too close to your babies, unless your running an air cooled hood that is.. i liked to keep my 250 about ten inches to a foot from the tops of my plants, especially at such a young and tender age.

just added a few

Sounds like over watering. Your roots need some time to dry out and breathe.

Yeah, those are way over watered. Even in those small cups you can tell by how they feel. Let it get nice and dry, like where you can lift the cup and you feel the difference, then give it a good soaking, then let it dry, etc.