Do you mix the cereal with formula/breastmilk? That's another thing to take into consideration. They may be taking in ounces you aren't thinking about if you do....which would lead me to not worry...if on the other hand you make the cereal with water or juice, then maybe try cutting back.
Also, how old are your los? My DD is 8 months and she has been on 3 solids meals a day for maybe a month and a half or so....she did great until a few weeks ago...then suddenly she started losing interest in finishing her mid-day bottles and we combined them. She went from bottles at 7, 11, 3, and 7 to bottles at 7, 12/1 ish and 7...with a snack and water or juice around 3. Sometimes I try to sneak in another 4 ounces if I think she's up for it, but overall I don't stress as she still takes 8 oz for each of her three bottles.