doctor: without any additional information, it sounds like you're asking about apples and oranges. your use of acidulated should have no bearing on rice and corn.
acidulated malt is used to lower pH (a chemistry adjustment). rice and corn are used as a source of relatively flavorless fermentables (recipe adjustment). one shouldn't affect the other.
if you're asking if you should add them all together to your mash, at the same time - the answer is yes. grind 'em all up and throw 'em in the mash tun.
are you using any minerals, like gypsum, calcium carbonate, epsom salt, etc? RO water is devoid of the minerals that yeast need.