Superthrive is fine, in VERY small amounts. The problem with superthrive is people look to it for a B1 additive.. but the B1 in superthrive is a secondary component to the more powerful hormone that makes up the bulk of its effect. Nathyl acetic acid is an organic plant hormone that forces rooting. The hormone 1-Naphthaleneacetic acetic acid (NAA) does not occur naturally.
It is very effective, to the point that overdosing with it will cause the plant to work on nothing else.. I only use it for transplanting, and I only use 1 drop for a gallon.