Female yellow lab breeding behaviour

[NICKOLAS]

hey guys so i have 3 yellow labs. 2 females and 1 male. Recently one of my females has gone dark in colouration, everytime she goes next to my male and spreads out his fins and goes dark then chases her. Anyways my female has started digging a big hole under the males cave. She now just sits in this hole which is directly under the cave the male is always in. Sometimes i catch them both in there then he just chases her out and sometimes he might be digging but its mainly my female digging the hole. I want to know if this is breeding behaviour or if its normal or anything like that. Its been like this for 2 days. I feel like the hole she dug is a hiding spot because everytime i walk up to the tank she swims to it. But then i see the male and her get close so im confused on what behaviour this is. I also do have ammonia in my tank which i have gotten down but still attempting to get rid of. A bit of cloudy water too. Is this causing my yellow lab to behave like this or is it breeding behaviour?