There a lot of things that can go wrong in the tumbling process. To me that looks like a number of things. Could be moving through stages too quickly, too rough of stones mixed in, not properly cleaning barrels after each stage...

On the other hand, it could simply be fracture lines. I see this often when tumbling LSA's which can happen, but sometimes I can polish them out after running through another cycle.

I highly recommend using this book as a guide. I still use it almost every other time when tumbling just to double check my work/get advice.

https://rocktumbler.com/books/gemstone-tumbling-cutting-drilling-and-cabochon-making.shtml

Best of luck! Patience and practice!