marigold varietus aggressive?

Platies are usually docile; poor water won't cause aggression in them. The only aggression I've witnessed is from males towards females during breeding. I've never seen any from the females at all. I actually had to get rid of a Red Wag because he was harassing an already-pregnant female to death. Are you sure that you have two females and a male, and not the other way around? It really sounds like two males harassing the same female, which causes her to hide. You can find pictures of the differences online; essentially the females have a fan-shaped fin and the males have the pointed gonopodium. Males are also usually a bit smaller, when they're fully grown.

If it is two males, you'll need at least three additional females. Five might be better, but I'm not sure if you have room for eight platies. (If the only other fish are the guppies you could get away with it as long as you are religious with the weekly water changes. Perhaps even up it to biweekly.) Either way, get some more females, but I'd say the most likely cause is a case of mistaken gender identity resulting in a bad ratio of males to female.

They are docile fish as they can live in communities. Usually when breeding platies, one should keep at least three females to every one male otherwise aggression can and will occur.

How are your water parameters? How large is your tank? Was it cycled before you added the fish? What other fish do you have, and how many? If you would answer those questions, it would help us in figuring out why your fish are suffering from aggression issues.

Aggression in normally docile fish can point to poor water quality. I recommend testing your water and performing a partial water change if need be.