12 inches - yes other plants.
And that is just a guideline. For example, I grew Eucalyptus and Pomegranate from seed started in February and they are both past 12 inches though I chopped ~ 4 inces from the Pom.
And yes - the plant starter solutions has in addition to Vitamin B, many micronutrients not found in any regular fertilizer.
In general, I would not normally use it to such an extents ... but at 3 $