Nutrients and Energizers sound pretty beneficial - and they can be! But, what the heck are these products!? Moreover, if you use the wrong stuff or an inappropriate bolus, you can do some major damage to your yeast! What you need to know about nutrient vs. energizer
Yeast nutrient blends typically contain a mix of trace elements and important molecules including inorganic nitrogen, organic nitrogen, zinc, phosphates and some other stuff that helps yeast grow and complete fermentation. Directions generally call for the addition of 1/2 tsp at the time of pitching. Energizer is not the same as nutrient - please don't use the lingo or products interchangeably! Energizers are indeed nutrient blends, but typically contain components such as diammonium phosphate, yeast hulls, magnesium sulfate, vitamin B complexes, and tricalcium phosphate. Directions generally call for the addition of 1/4-1/2 tsp at 24hrs, 36hrs, and 48hrs after pitching. Please be aware that diammonium phosphate (DAP) is toxic to yeast in high concentrations, so be censorious in selecting a nutrient blend for use in starters or at pitching that does not contain DAP. Use DAP-containing nutrients (aka "energizers") in subsequent nutrient feedings (@ 24hrs, 36hrs, and 48hrs).
GoFerm and Fermaid K used to be available. Now they are not. In their place are Nutriferm and Nutriferm Advance. Use them the same way you have been using GoFerm and Fermaid K, respectively.
I typically find that addition of yeast nutrient is not often necessary unless I'm brewing a high-adjunct beer or a mead or a wine. However, serially feeding your fermentation nutrients and energizers can help avoid those dirty diaper and rotten veggie smells that malnourished yeast sometimes produces.
Yeast makes beer, wine and mead, so please treat them well.