Dear gardeners,

I need some help to identify a problem of a few seedlings that I have.
I am growing some black locust (robinia pseudoacacia) seedlings from seed. Currently they are about 3-4 weeks old. They are planted in a coconut choir that is enriched with fertilizer and vermiculite mixture (50:50). I water them daily very small amounts. I had 3 of them and then one of them fell over. After inspecting I found that the stem at the soil level was damaged. It looked as if it was chewed off. Here is the image of what I recovered:

After inspecting the other two I found similar but smaller wounds on the stems. Here is the seeding with bigger wound:


What could have caused this?

One other note:
because all my windows face north I am supplementing natural light with one growlight (11W compact fluorescent lightbulb).

Hi DeXodus and to NGA

Well, the first thing I thought of was damping-off disease. However, after seeing your pictures, my guess would be a hungry mouse.

Art