just a question about growing

[xNoa]

i had four beautiful plants growing in my yard and in a matter of a few days two of them turned into males and were covered with seeds. Can anyone explain why this happened and is there anything i can do to prevent this from happening in the future.

were they already female?
if they werent thats just what happens.
if they were, then theyve 'hermi' where they go male through flowering which can be caused by stress of the plant, not enough/too much light, heat, maybe transplanting stress, or the strain youre growing might just be known for it