Well, your red circles are more visible. 

  Flat worms can change shape but they all have a similar shape.  I can't tell from the pictures but even if they are flatworms, I would leave them alone.  I have had infestations of flatworms before a few times and all those times, they disappeared and never hurt anything.  Once there were so many flatworms I could hardly see my rock.   

   I personally would not add anything to eliminate them because if it has the word "eliminate" in the description of how it works, it is a poison of some type.  It just depends on the dosage as to what it kills.
Flatworm exit kills flatworms and I assume all worms and a large part of the microbiome in a tank are microscope worms.  But thats just me and I wouldn't use any chemical in my tank for anything that I can remember.  Good Luck