Ok thats was alot to read so ill prolly forget he things im spose to answer so ill try my best here.The system you are using and the light aint the problem..trust me i got the same set up.By the sounds of it yes your problem with the soil attempts is you didnt fertilze..you should give it nutrients after about a week or 2 and walmart soil isnt really a factor cuz ive used walmart soil plenty of times,but now i use fox farm.Also when you were growing in soil you should water every other day but not a whole lot..or some ppl even only water when the top of the soil looks dry.As for the hydro grows..the nutrients aint the problem becuase i use them nutrients threw my whole grow.Your ph should be around 5.5 least thats what i keep mine at.And as for your light i keep mine 43 inches away from the top of the plant...i dont know if that is to far but it seems to work great for me.And watering them 15 minutes every 2 hours may be to much i run mine at 15 minutes ever 3 to 3 1/2 but remember that your roots dont stay wet for very long if your using your lil rock things they give u to grow with...not sure what they are called.And there is really no need to buy a mh light as for your question bout ppl talking about a cfi light....they are talking about cfl's wich are compact flourecent lights.I use the cfl's for veg stage becuase you can keep them 3 inches form the top of the plant at all times and they grow nice and good growth rate.Mh bulbs are better for veg stage becuase they will give off more lumens wich meens more and faster growth for your plant but cost more to run and are alot more expensive then say your 42 watt walmart cfl's.

Ill explain how i use my hydro kit.When i am germinating the seeds i use the rockwool cubes that i got with the kit and i put the seed in the rockwool and get it wet...not to the point where it is soaked but just wet.Then i put the cube in a ziploc bag to hold the moisture and put it in a dark warm place and check it every other day misting it if it gets to try.As soon as it sprouts i take the rockwool cube and i place it in the grow rocks in the hydro kit and put my cfl lights 3 inches from the top of the plant.The lights are on 18/6...18 hours light and 6 hours dark.I dont give the plants any nutrients during the first week to week and a half..just water with a ph of 5.5.After the plant gets out of the seedling stage n hits the veg stage wich is about a week to week and a half i start adding nutrients but not the full amount..only half the amount or sometimes even a quarter of the amount shown on the instructions on the labels.As the plant gets older i gradually increase the amount of nutrients it gets and by the end of the first month its at full nutes.I keep the plants in veg stage for 2 months wich is pretty much the standard veg cycle or untill i see signs of preflower.When i see the signs of preflower or when the 2 months is up i turn the lights off for 24 hours n then switch the light cycle to 12/12.The first week after switching the light cycle i still feed it the grow nutrients n then after that week i switch to the flowering nutrients wich is the bloom and micro.I also change the resevoir about every 2 weeks to keep the water fresh and the nutrients available to the plants at all times.Try to give the plant as little stress as possible to by making sure the ph is right and having nutrients for the plant n when the light is off...dont disturb it.Now flowering stage usually last 8 to 10 weeks depending on the strain but i usually go by the color of the trichomes.When 75% of the trichomes turn amber its ready to be harvested.Also before you harvest you have to flush the plants off all nutrients so 2 weeks before you harvest your plant change the resevoir and only give it ph correct water and change the resevoir 2 or 3 times...this gets all the nutrients out n doesnt give ur bud a bad taste n harsh smoke.

Im not sure if ive helped you out any as i may have confused you so if you have any questions or dont understand just ask ill be glad to help ya out...and no worries i killed like 8 plants before i finally figured it all out to..but we learn from our mistakes.