If you have tons of plants and the tank has been fairly well established then you do not need to feed daily. You should also use shrimp specific foods that do not break down in water so you can take them out after 2 hours. I personally never leave uneaten food for a very long time. Shirakura Chi Ebi and BorneoWild Bebi are great foods if you are scared of your babies not surviving.....both are actually "good" for the water quality if dosed within reason.
In terms of you planaria question. You would know if it's planaria since they have triangle heads and they move fairly fast around the glass etc. Once again, if you are feeding too much then you definitely up your chance of getting some planaria. What you describe does not sound like it though.