Cultural differences - green vs. mottled leaf Paphs.

[shakkai]

I have a problem that I can't seem to figure out. Given my cooler growing conditions, I had thought that green strap leafed Paphs would be easier for me to grow than the mottled leaf types. In practice, all of the mottled leaf types have been doing really, really well. new growths, spikes, the lot. However, the only Paphs that have died on me have been the green leafed types - and the others don't look all that great either. Of the group, only three seem to be doing as well as the mottled leaf ones: a charlesworthii, fairrieanum and a seedling St. Swithin.

My question is: what other conditions should be different between green leafed and mottled leaf types, besides temperature? There has to be a reason that I'm not doing well with the green leafed ones!

I know that the green leafed types like higher light, so they are closer to the window. What else can I do?

Any ideas?