Listen to his advice….add some additional perlite and EWC at the start. That will carry you into flowering (if growing autos). Just water it…and I always ph’ed my tap to 6.6-6.8.
Around week 5 or 6 (as the plant is exhausting the amendments) you can do any number of things…the simplest being to top dress with more of the same (ocean Forest and EWC)…..or do what I’ve done and top dress with a dry organic fert. and EWC. I use Gaia Green but wouldn’t hesitate to use others.
Other than the occasional dose of ReCharge, mycos, stump tea, etc etc., for the microbial action, all that’s needed is water.
I’ve never had to give cal mag…I guess my tap has what’s needed in that department…..others do need a touch of it.
Believe me when I say there have been more grows ruined by dumping a dozen different liquid nutes on the plant than you’d believe.
Keep it simple, give the plant what it’s used to and acclimated to and you’ll be good to go.