Try a hard reset on your lights and delete them from the app. This fixed my issue with connecting to the reef led at my work. I would say if this fixes it just get another reef LED 50 and use your other one.
If my understanding that your tank dimensions are 35x23x28in, You have several options. I personally would go with either 2-3 ai prime 16hd, 2-3 kessil a160we, a reef brite fixture or 2 kessil a360we. I think these are all going to give your a nice spread and color. There are more expensive options like radions and cheaper options but I will list some of the in between options below. If you would like some more recommondations on the higher or lower end of price let me know. BRS has videos on these lights of you want more info.