Your two monitors are from different habitats---sav's are from arid regions while Nile's are from riverine habitats so their humidity needs are quite different.
Aside from that,I still wouldn't keep two different monitor species together in the same cage. If you have no other option at this time,at least make sure that both animals are getting enough to eat and the food is not being taken by the most dominant animal.
Also basking lights and ceramic heat emitters are a much better source of heat than heat rocks. I lost a Nile monitor to a heat rock mishap.
Good Luck, --Kevin--
German Tour Guide: You vill find more on Germany's contributions to ze arts in ze pamphlets ve have provided.
Brian Griffin: Yeah, about your pamphlet... uh, I'm not seeing anything about German history between 1939 and 1945. There's just a big gap.