It could be one of two problems... 1) It may be under fertilized. I was thinking with biobizz you were supposed to use like one tablespoon (15mL). And during that initial stretch the plants use alot of nitrogen. Or... 2) It could be a pH inbalance which is locking out nutrients. I would say it just alittle underfertilized but test the pH first so you don't possibly just make it worse.