Hun, my first DS was never great at evening meals, and TBH it is still not his best time of the day for eating. I think some kids don't feel like eating at the end of a day, whether it's because they've already had enough, or are too tired. When DS wasn't eating much at all for dinner, we used to give him "lunch" food for dinner so it didn't matter if he didn't eat a lot, save some of what we ate, and then give it to him for lunch the next day. This seemed to work better as he was still getting a good balance of foods but he was able to eat when he wanted to.

It is worth noting that eating most of your food earlier in the day is actually healthier - eating the "fuel" before you burn it up during the day. So maybe these kids are doing what comes naturally!