What exactly is RO water and what is it's PH value? I've seen an RO water system on eBay but it doesn't say that it can be used for producing aquatic water and makes no mention of water PH changing.
I know nothing about RO water basically..
RO is a mechanical purifcation process that removes 'contaminates' from the water. In theory it should produce a neutral pH (7) or just slightly lower.
There are systems specifically branded for aquarium use but to be honest I dont know if they function any differently to the ones you have found on eBay....I doubt it though.
I think in short term there is no 'quick fix' to the issue your GBR's are facing. Bogwood, peat, RO will all take a while to have an effect on your water. Maybe you could return them to the LFS if you are concerned about their health? Then you would have time to set up and stabilize the tank pH before re-introducing GBRs.