double foul?

[RX Ref]

Last night, girls tournament, A1 at the line for the 2nd of 2 FT. A2 and B1 begin sticking there arms in the lane and end up smacking each other fairly hard. I blew the whistle and called a double foul and went to the ap arrow. At the half, my partner said he would have blown the whistle and given them a warning. I also thought i could have called a a double T since it was a dead ball- I'd like to get some opinions....