First time in coco

So its my first time in coco (botainicare cocogro) and im using house and garden a&b for nutes. The grow shop said its a great 2 part and i would never turn bacK. now heres the question, what additives should i use that wouldnt break the pocket? I have a bottle of calmag if needed but i also have epsom salt. Atm im in veg and i like to keep it simple. During flower ill use mother of all bloom (pk booster) and sugars ( prob molasses). think anything else is needed?

you use it as a filler and water holder. u have ti add all nutes coco has none