1 rig 3 cards 3 miners

I have 1 mining rig with 3 different cards. RTX 2060, GTX 1070, and GTX 970. On ¨What to mine¨ it tells me 3 different coins to mine when you take the cards individually but when taken together they give me another coin. Question: is it better to mine 3 different coins or to mine just one coin at the same time. To me mining the most profitable coin for each coin seems logical but i don’t know if mining one coin with all 3 cards is more profitable. Thanks to all who can help me understand.