peppers

Most likely the ubiquitous slug or small snail. Creep out with a torch at dead of night and you will probably catch whatever it is doing it!
If it's eaten the top leaves, as the advice is often to 'pinch out' peppers to encourage side shoots, perhaps it's done the job for you.
I grew 'Bell boy' last year, but I find I get better results with seed taken from large red or yellow peppers bought in the supermarket. Whether they are from F1 plants, I don't know, but we were lucky to get some really good plants and peppers.