I’ve got a couple of Yongnuo flashes and radio transmitters and I can’t fault them. Frankly the only speedlight upgrade I could see myself doing is a half dozen canon 600 RTs. If you have three flashes I would get a four pack of the rf-603s or a four pack of yn-622cs if your flashes will work properly with the ETTL commands from it. The 603s can be a little annoying if you try to put a speedlight on top of it as there is no screw fastening to keep it in place. They don’t fall off if they are put on the camera at least. Get yourself two cheap light stands and two white shoot through umbrellas. The Westcott ones are pretty good and cheap. It should all come to around $200 if you shop around a bit while still getting decent stuff.
The main problem I see with your shots is they are over flashed with a direct flash. Direct flash can work really well but mainly if you are a paparazzi or for portraits if you get a ring flash instead. A decent set up would be two flashes behind umbrellas up and at an angle with the last speedlight from behind to give a bit of rim light. Obviously that is a completely generic set up that needs changing as circumstances change, especially outdoors with the sun.
Second problem is that a lot of your shots are overexposed. There is high key and there is over exposed, yours is the latter I’m afraid.