Frogspawn need very low flow in my opinion. I mean you need enough so that they sway a bit and they can get rid of waste and stuff but not much more than that. Should never see heavy flow like you see sometimes with torches where it has them jerking back and forth pretty hard. Little bits of the tentacles falling off in my experience is not all that unusual when they are being handled especially after shipping, but the chunk yours shows to be missing is not a good sign. The smell is also not a good sign at all and points to some infection is likely. I have been having success with apparent wall frogspawn and hammer issues the last several months using Kanaplex and keeping them in a "dip" for three days. A common suggestion is an iodine dip (which in the past was always my goto, but never really felt like it made things better for coral already in poor health).