Depending on the shape of your cocker spaniels eyes, eye stains might not be uncommon. Some people will try something like “Angel Eyes” or a similar product and that might help. I wash my cocker spaniel’s faces with a wash cloth and warm water daily and I seem to be able to keep the eye boogers under control.
I’ve been thinking more about this and I too would suggest you consult your vet. Cockers can have eye conditions that may contribute to the discharge from your dog’s eyes. They can have dry eye or allergies which can be managed with drops. Sometimes they have eyelashes that may rub across the eyes. If that’s the case, your vet can probably use a laser to remove them. Anyhow, it’s worth getting it checked out.