There are several good pellets for chins such as Oxbow, Tradition, PRCS, Manna ProSho, Nutrena, etc. You will find a difference of opinion for the "best" pellet for chins. I don't think it's a good idea to offer them a couple of different feeds all the time. Although I have offered all of my chins a pellet or two as a treat of the Beaphar which are extruded pellets from the U.K.
It's good to read up on chin issues and be prepared but to panic now while your chins are healthy is not good for you nor them. In my experience, I've had 2 chins with malo and both had to be put down. My first chin I bought from a pet store so I don't know how old he was when I got him. He did not show signs of malo until 2 years after I bought him, so I'm guessing he was at least 2.5 to 3 years old when he first had the malo symptoms. With my 2nd chin with malo, I bought him from a breeder and he was 1 year and 11 months old when he first showed symptoms of malo. I think that malo can show up on chins at anytime but I've heard they show up more often on pet chins between 1 and 3 years of age.