(White Widows) Can I Transplant Into Different Medium? What Medium is Good?

My four White Widows are almost three weeks old and I have them currently in cheap local store bought soil and they are looking good. I'm about to try my first and only transplant for these plants and I want to make sure I'm doing it correctly.
Is it safe to transplant them into a different and more viable soil like this one I looked up -- "mixed with 50/50 soil/Worm castings (Organic source of N) then dither that off with vermiculite and perlite (To cause air pockets in soil and prevent packing) then add 1" gravel to the bottom of your pots for drainage." ???

Thanks in advance!

Sounds like a perfect idea. Get them that organic goodness. Transplant away!

If you're asking if it will hurt your plants by transplanting from one type of soil to another, so long as you're transplanting them into good soil, the answer is "no".

Go right ahead and do it.