Angelica,
I have a picky eater too and I like to cook healthy meals and have a balanced diet. He is probably going through a growth spurt, maybe feeling ill or just simply bored with the food. You obviously have gotten him to eat more than mine at 2yrs. Mine liked Honey bunches of Oats for breakfast and Oatmeal for quite some time and out of the blue he just stopped eating it. Of course I panicked, because now what do I give him for breakfast that he likes. It so happened I introduced a different type cereal, Cherios, and he loved that for the time. I later reintroduced his favourite Honey Bunches and he started eating it again. Also, you mentioned he eats well at daycare, which is a sign that the food in his mind is "varied and different". My son will eat the SAME mac and cheese from my M. and will not eat mine. He also tends to prefer "restaurant type" food, like if we have KFC, magically he likes coleslaw, but I can't get him to eat veggies at home. So it may just be that he is bored with the choices, the taste and/or the presentation of the food, since we all cook differently. As for a balanced diet, I would go with his flow for now. I think you're doing great with the choices you have before and if it's not everyday eating junk, having chips shouldn't hurt, also having chicken nuggets for breakfast. As long as he eats it, who cares when, right. One more thing, try giving another alternative to milk/dairy or adding ovaltine or cocoa to mix it up a bit. Good luck!