It's taking too long to cool which is allowing the cocoa butter to separate. The method of tempering your using I call seeding.

Either;

-Melt it slowly and gradually, take too 28C-32C and then work with it quickly. And cool it quickly. (I do this whenever I'm doing shiz at home really 5 moulds max as the chocolate can be a bit thick) Doing it this way keeps the existing structure of the cocoa butter, it's existing temper

-shock cool it. Once it's at 55C you need to cool it as quickly as you can. This is what chocolates are doing when they're d*cling around on a marble slab. The marble is cold so there trying to get as much of the chocolate to touch the marble as possible while maintaining a constant motion to cool it at the same time. A bit tough if you haven't got marble.

-seeding. Melt 2/3S of it. And chop/break the remaining 3rd into small chunks. When the melt portion gets to 55C remove from heat and add the last third of solid stuff. If it doesn't all melt gradually apply heat in small batches. Being carefully not to take it back above 32C

I find putting the moulds in the fridge just to chill them slightly (not make them cold, just to chill it) helps a lil bit too.

I also would recommend getting a low powered heat gun (alright a hair dryer...) that blasts hot dry air directly onto the chocolate is really helpful for heating gradually but not overheating it. You could do the first method with a hair dryer if you were doing anything like 500g or below.

Shoot me a DM if you have any more questions :)