I have grown tomato, pepper and other vegetable seedlings indoors for years but I have never seen this situation. Something is literally cutting off the cotyledon leaves on the young seedlings just leaving the stem sticking up. It is not damping off and there is no leaf debris. I see some small gouges in the soil but no evidence of mice or other large creatures. I suspect some insect but haven't seen anything in the seed room. This is a pretty contained room that is heated with heat mats and grow lights. I use special soil and always disinfect my equipment each season. Thoughts???