UndercoverGrow is right, dont give up. If I had given up every time someone told me to, or every time someone talked shit about my grow, I would have missed out on a lot of knowledge learned first hand, and wouldn't be nearly as cool as I am now
1] Containers. I would get rid of those friggin plastic grow bags. They don't looks nearly big enough, and even if they are big enough there is no support, harder to move around, soil moves a lot, roots can break, they just look like some shit people invent to try and make money basically. Use 5 gallon or 3 gal buckets. 5 gal is my go-to bucket. If you want to stick with soil that's awesome, but Hempy Buckets are the fuggin tits.
Briefly I will outline this;
-Take a 5 gal or 3 gal bucket - Make one, 1'' or 3/4'' hole drilled on the side, near the bottom, 2 inches above the bottom of the bucket.
-cover this little hole with screen mesh so you grow medium (vermiculite) doesn't fall out, and fix in place with epoxy or with some little screws.
-fill your bucket with vermiculite ( I wash mine before use ) Medium Coarse grade should be good, some people put the really chunky grade in the bottom, and then finer up top, its up to you
This is a passive hydro system. The vermiculite provides excellent drainage, but will not dry out too quickly. Every time you water/feed, the water will moisten the vermiculite, and pool in the 2'' at the bottom of the bucket. This will keep the bottom more saturated, and the roots will be drawn towards that "reservoir" (bottom 2 in) in the bucket. You will not have to worry about over-watering because of the excellent drainage, and because of the reservoir at the bottom - you will be OK (once the taproot has made it there) if you forget to water for a day or two. There are many journals and articles on Hempy Buckets you can read.
2] Air movement. You need adequate ventilation and exhaust for your HID lights and hoods.. if your temperature is 77 deg, then you are probably OK on that. BUT you also need air circulation within the grow tent itself. 1 or 2 oscillating fans would help your plants exchange gasses better thus driving photosynthesis more quickly, and also strengthen your plant stalks.. and better/bigger stalks, as we all know, can hold better/bigger buds
3] Monitoring pH. When preparing your nutrients/water, if the pH is down around 5.5, this is OK, remember that pH will gradually rise over time. The minimum pH your water should be is 5.5, the max it should be is 6.5. I would shoot for 6.0.
If you have a little extra cash (180 or so) Tri-meters by NutraDip are really really useful. They not only measure pH but also water temp and more importantly PPM - which is fertilizer level. Then you would be able not only to determine what relative amounts of fertilizer you are using, and compare with other peoples grows, but also to record your own feedings for more accurate records and learn what certain plants prefer.
4] Continuing with soil. Your plant isnt that bad dude. My plants have looked way worse. All things considered, your problem could simply be over-watering. I would water once every 2-3 days really well, and let it reallllllyyy dry out. Be patient. In drier conditions those roots are going to stretch out and look for water, which is what you want. And as the soil dries, it will rise in both oxygen content and pH, giving the plant a 'full spectrum' of environmental conditions for it absorb nutrients and whatever. This will be good.
A rule of thumb is to stick your pointer finger in the dirt, down to your second knuckle. If it's completely dry, you need to water.
It looks like your soil mix already has some vermiculite in it, but I dont know how much, so just remember the more vermiculite in the soil mix, the more often you should water. If its only like 10% vermiculite then just treat it like soil. 20-30% you probably need to water every other day.
Sorry for the long list, but wanted to cover all the basics. Good luck brotha