White Rhino - Slow growth, yellowing and dead leaves

I have 3 White Rhino plants (out of my original 10) grown as follows:

Soil - Miracle-Gro Organic
Lighting - 400W HPS, Air Cooled, on 24 Hours a day, at 18 inches above
Environment - ~75F-80F
Watering - Spring Water w/ Miracle-Gro Tomato Food, every 5 days
PH Range - 6.2-6.5
Design - Hydrohut 4x2, 6" fan for the light, 4" fan for air circulation on a thermostat set to 75F, 12" Pots

They are growing very slow, they are only 6" tall after more than 3 months of veg! The leaves are yellowing, then dying off, new growth lasts about 2 weeks before repeating. I've had 7 of the original 10 slowly die off, and I've tried just about everything. I'm out of ideas and could really use some help.

3 months of veg??? trash em, they're stunted and they won't be worth your time. they can be brought back, but you'll yield very little. it wouldn't be worth the power bill.

miracle grow soil + miracle grow every five days = way too many nutes for young plants!