i recently got 2 female platies (to make sure there were nto going to be any babies) and al;l that they have done is lay on the bottem of the tank. should i be concerned?
Yes I would be concerned. What are your ammonia, nitrite and nitrite levels? Are the holding their fins close to their bodies?
Also, getting 2 females doe not ensure there will be no babies. The only way you can ensure no babies is to get 2 males. Female platies generally come from the LFS pregnant unless they are kept in female only tanks. They can hold sperm for 5 months so can give birth that many times after exposure to a male
I would do a 40% water change with dechlorinator ASAP, you also need to test for nitrites as your tank could be cycling which is bad news for any fish in there- both nitrites and ammonia can be removed with water changes although you shouldn't take out more than 60% at any time and do not clean the filter out in tap water.