You know, if it's that "muddy" and dirty, you might as well remove all the water, besides, moving with even 20% water left, plus substrate is going to put a lot on that tank glass... I say drain it all, start over with fresh rinsed substrate and then put the LR
back and start a cycle... that way you arent setting yourself up for more problems.
You can trade the star or set them up in a smaller tank temp for a few weeks while you recycle...
That's what I would do... just my 2 cents
Good luck and keep us posted