I have killed plants by giving them too many feedings of rooting hormones. The plants expended all of their energy producing roots, became totally root-bound, exhausted, and died.
Since then I have learned that one application is plenty.
The root stimulant sold under the Vigoro brand name is a good product, those sold under the Schultz brand name are weak, and the "SuperThrive" product can overstimulate your plants and should be used sparingly.
While we're on the subject, you should know that "vitamin B1" is a hoax. Only one study with a positive outcome was ever performed on this compound, published, and then retracted 9 months later when a multitude of studies showed that the results could not be reproduced. To save face, the companies selling "B1" did not change their label but added several beneficial nutrients to the mix so that customers would see a positive outcome.