I'm no expert, but gibberellic acid is a hormone that is used differently by different plants. You can get supersized pumpkins and melons by using the stuff at various stages of the plant's growth but it doesn't work for all. With many plants it actually has a negative effect. My understanding is that it can be used to induce male flowering in cannabis -- unless you want hermie seeds you probably don't want to use it unless you know what you're doing.
Colloidal silver is just microscopic silver particles in a water suspension. It was used back in the day as an antibiotic before the good antibiotics were invented. I'd imagine it would have similar affects on plants in keeping the little microbugs away, but there are far cheaper things available like neem that will do the same stuff for less cash.