Crops are breaking magically

UPDATE: Found issue, there were no light sources above crops...

 

So, I play on a realm.

 

I have created a potato/beetroot and a wheat farm, underground. They are semi-automatic, so when a lever is flicked, water runs down the farmland and collects the crops (then I replant them).

However, crops seem to break by themselves. In the fields, there is a patch of farmland which breaks the crop magically by itself and drops the crop as usual. This happens in the same patches. There are no villagers nearby, and I was playing by myself.