I think what the OP is saying is that they originally left feedback right after they received the eggs that relates to shipping, and now that the eggs have hatched a month later they would like to add another comment about the eggs hatching.
As far as I know, the only way to leave "more" feedback is just as femmefan1946 suggested: add a response to the feedback that the seller left for you.
In the future, if possible, consider waiting to leave feedback until you make sure something you have purchased has arrived, is complete and as described, and works as intended. You have 60 days to leave feedback, so in most cases you will have plenty of time after your purchase arrives (except if you purchase from China, which is notoriously slow, especially recently).
Now, depending on when you purchased the eggs and how long they took to arrive, 60 days may not have been enough time to wait a month for them to hatch before leaving feedback, but again, you can always leave a response to the seller's feedback.