All these comments and no one mentioned RH? For shame!
If your RH is above 60% the plants will thrive on temps in the mid 80s, but they will suffer if RH is too low. This is independent of adding CO², although CO² will certainly bring big dividends in a high temp, high RH environment.
From the sound of things, you have an RH management problem as much as a temp problem. Adding some daytime humidity will help both considerably, I use a swamp cooler to maximise the effect.
Another thing to do to help manage summertime temps is to extract air from the room as close as possible to the lamps themselves; this minimises convective and conductive heat gains in the space. I used a length of 8"exhaust duct and placed the opening right behind the socket carrier of my wide open adjust-a-wing and the room hardly warms up at all under the HPS thouie in it.
From both a heat management as well as a lighting engineer's perspective, it's a fool's errand to blow cooling air on bare bulbs. Try to avoid it as much as possible. Sucking the exhaust air from nearby is another thing and is just as often recommended.
