When to transplant?

when i can pull it out without the substrate falling apart... generally when the canopy is same diameter or even slightly larger than the solo cup. roots help hold the plug together... if the roots aren't holding it together, it doesn't need more room, yet. unlike others i have a light feed right from the get go in teh substrate... that way as i irrigate it slowly rises up to full strength by 2nd or third irrigation with runoff (soilless grow conext) you have top-dresses, so you need to ramp up as what you added is used up or otherwise leeched out of soil. 2 things i see -- when you irigate get the whole thing wet.. dry spots up top make me thing there may be dry pockets underneath. dry pockeys underneath *can* lead to buidlup. Also, use more perlite or vermiculite et al to improve drainage of you soil. up to 50/50 soil to whatever is added to improve drainage. (70/30 wiwth coco cause it holds less water per volume) it may incease rate of fertilization, which is also a positive as long as it isn't burdensome. feeding more on demand genearlly has better results. (you'll still add rughly the same mass of vaious ferts per week o month.. the rate of application just changes.. concentration given should change with that..)