Newbie with a Yellow Spots on Phal Leaves

[camille1585]

Don't worry about all the questions, that how we all learn here! Your game plan is fine.
Your mix is fresh, so you can re-use it. Most of us don't use the marbles/rocks at the bottom, but it certainly won't hurt any if you do, and at least you are sure that the drainage is good.
For the pot, either you just rinse it out, or if you like to be cautious, use a little bit of bleach. If it's a clay pot though, you'll need to rinse it very well in that case.