Reds OPS against lefties is .708, third worst in the league. Against righties it is .784, third best in the league.
Phillips has hit over 20 homers this year from the right side. Good for a middle infielder. Gonzo's .792 OPS is good for a shortstop. Nobody else has done much righty this year, particularly if you focus on power.
Possible ways to address this?
Reds can get add a power hitting righty. Usually this means an outfielder or first baseman. The Reds currently have all lefties in these spots (platoon at first) with lefties Votto and Bruce in the wings. If they do this, which current player gets replaced?
Reds can try to get an offensive catcher who hits right handed. If the Reds had a big hitting righty catcher this problem would be solved. Not that easy to find though.
Reds can replace EE. There are power hitting third basemen around. EE may or may not get there, but he has had a serious lack of extra base hits this year. 24 altogether in 370 at bats.
Reds can platoon more. A possible additional platoon would involve Hamilton. Not advocating this, but it could help against some lefties.
Reds can say it doesn't matter, the team needs pitching, ignore hitting against lefties. Eventually righties will come up from the minor leagues, although guys like Stubbs and Frazier are still years away.
Longer term this remains a problem if Dunn, Votto, Bruce, Hamilton are all starting players. The same considerations would apply.