ok so i got worried about my discus cause there colours went quite dark, i asked the fish shop that and the guy said that thats normally not a problem and also a sighn of the discus wanting to mate and especially if the temp goes up. now i have 2 and one eats and the other doesnt and the one that eats always hangs around the other and sometimes if she swims off he'll swim over to her and sometimes even chase her. is this a sighn of it wanting to mate??