Well, lots of strange advice here. I have re-vegged a lot of MJ plants, some many times over. I have not seen re-veg plants produce smaller yields. If anything, they tend to produce larger yields. It depends on light and heat though. I do not add any special water or vitamins or soil or much of anything else. Not needed. What I do is... I cut the primary buds and colas in progression over several weeks from top to bottom as they mature. I then cut all the colas/flowers off the plants in a last harvest, and leave as much leaf on there as possible. This can be tricky with some strains. Then I feed them half strength higher nitrogen water soluble fertilizer, like 30-10-10. Then I park them outside in the sun if it is warm and the days are longer than 14 hours (like in April through August here in Oregon), or indoors under HID MH lights 20/4 or 24/0. I have had 100% re-veg with strong post-bloom plants in 5 gallon pots or larger. I tend to grow in pots so I can move the plants around for several reasons.
As I have said in other posts here, I grew 4 strains last year under lights in the winter 24/0 until April 1, and then set them outside where they all started blooming. They continued to bloom strongly (no re-veg) through June when I harvested them. I then left them outside in the greenhouses and fed them, and they all re-vegged within 2 weeks. They then grew much LARGER and taller, I potted some of them up from 7 gallon to 15 gallon pots, and they grew like mad and started blooming in August-September (depending on the strain). I started harvesting in late September, and moved them back under lights in October because of the early rains and cool weather here this fall. After harvesting outside or finish blooming them under the lights and harvesting, I fed them and re-vegged them under HID MH lights (400 Watts) 24/0. It took about 2 weeks before they were roaring along again. 100% re-veg. Some put out popcorn flower buds at the bottom, but I just cut those off.
These strains included: Blue Dream (Santa Cruz cut), White Widow (Dutch cut), GDP (Santa Cruz cut) and OG Kush (Ghost cut). Easy peasy. I make my own soils, basically 1/2 silty loam from my property, 1/4 rotted composted bark, leaves and sawdust, 1/8 Perlite, and 1/8 charcoal/biochar and ash. Again, nothing special, except my soil is riddled with various types of mycelium (fungus) that fruit on my property, and they are symbiotic with most plant roots. I do not root prune. I have cut many stems for cloning along the way during veg mode. My advice form my experience: leave as much leaf as you can, remove all the flowers, feed, and give them lots if light and above 75 deg. F. heat. They will do the rest.