Sorry to hear of your troubles.
Everyone has pretty much covered all the bases, and I never seen any flatworms in any pic.
After you explained everything with your recent setup it appears to me that your tank is just too new for corals. Don't take offence but you really need patience in this hobby and by the posts you have put up you might be lacking that
Not putting your phosphate and carbon reactors on line wouldn't have caused this either.
On another post you mentioned vinegar dosing? Still doing that? You by chance didn't over dose did you? There's also guys that don't use GFO or Rowa when dosing.
Good luck and hope you get this stuff figured out. And maybe put off getting any SPS for a while.