Yep, looks like classic MG soil results.
I found this site right after starting my plants this year. All my previous starts had the same issue as you have. I just purchased some Ocean Forest and Happy Frog with some perlite to mix in for added drainage.
It’s too late for me to repot what I have, but I’m hoping to get a female that I can clone and place in it once the roots get established.
We can grow in MG soil, but your success will be in spite of your soil.
Good fortune with your transplant!