Mine breed and they are large. In my experience the male will defend the fry until they are 1cm plus. Mine even try to attack my hand when I feed the other fish frozen food. The ones I grew out were about 5 cm in size and have not bred. What size are they?
If they breed at 4 months I would be surprised, most cichlids take longer to breed. I might be wrong as this is only my opinion, mine started breeding at about 7 cm and that was at about a year of age.
Hope this help, anyone with different experience welcome to give their input, we all here to learn.