I need advice

I was placed gold 2 last season and i peaked at gold 3 this season, (near the top 180k in NA). After a long incredibly unlucky streak of afk/dc team mates i managed to fall down to gold 5. My biggest problem is not my mechanics or game decisions, but it is infact trying to get my 1/10/3 top laner to stop diving into the enemy team 1v5. I figured the climb back to gold 3 was going to be rather easy because i win about 90% of my lanes, i roam properly, and i try my best to get the other lanes fed aswell. But the only thing i can't seem to control is the 5/11 top laner diving head first into the enemy team 1v5, or forcing a baron when everyone on their team is alive. I also have this problem with my adc's where they decide they want to be the front line and try to kite inbetween the enemy mao'kai and braum. any tips on how to get them to stop?