Hi,
I have experienced this with my late summer cauliflowers! Nibbles all over the flowers buds and, rather grimly, droppings too 
I rescued a few but the rest have gone to compost unfortunately. Can’t say if it is mice or voles etc. but the veg are meshed so it is not pigeon damage and I saw ‘something’ mouse like on one of the heads the other day.
Traps might be a possibility I suppose?