new beardie

Question
We had a beardie Dumbledor (5 months old) and yesterday added a new - what we thought was a - girl to our family she was very docile in her old home ( both dragons are from the same clutch) we thought we had a boy ...still do. And the new one should be a girl.  Our original male is about 1/2" bigger allover than the new one and yet the new one is the one bobbing her head and she has turned totally black  Dumbledor( our original lil guy) is usually the snappy one with us but with Tonks ( our new beardie) He does the waving arm thing.  
They chase each other occasionally around the tank ( which is 48x16x18 but no blood letting- I am worried because she has so drastically changed colors - she was orange and now her whole body os black like her beard...she is always in fight position although they slept on top or side by side- is this just normal getting to know ya beardie behavior or do I need toseperte them and introduce them slowly ( my problem is that the only other tank I have is a 20 gal.  I can not tell completely the sex of either dragon - she looks like the pictures of the female under her tail but??? and now I question his sex because he is so submissive. Oh - this was a new tank to both dragons- I bought it and placed them in it together to give them even ground.I have a UVB light in one corner and a baskinglight 75 watt and a heating pad under the other end is this addequate? The person we bought the dragons from is a teenager from our church who has just started raising them so I don't always know if she has all the answers. We love our lil guys and just want them to have company and be happy!

Answer
 You need to keep them separate, especially now.  Five months old is when they are sexually mature but not physically mature.  Plus they are territorial and should always be housed alone.  And siblings, male and female will not recognize each other as such.  You certainly do not want them mating.  Please separate them today.  
 In the wild, they live alone.  The only company they will bond to is their human, with enough attention.