Dracula leaf tips

[VickiC]

Hi,
I have had this Dracula Sodiroi just a few weeks and recently the leaf tips started turning brown ( ..I'm not a good photographer..sorry. Awhile back, I read somewhere the reason that this happens, and it may have been here on OB, but I can't find the thread if it was ?? The plant looked fine when I rec'd it from Andy's Orchids, so I'm sure it was me who caused the problem. When I rec'd it, it was potted in all sphag but I transferred it to standard orchid mix (bark, charcoal, etc.) simply because I can monitor the dampness better.....it's a little harder for me to judge when to water a plant potted in 100% sphagnum. I have had good results when trying to grow roots in it, though, but these Drac roots looked fine. Do you think I should repot it back into sphag as it was when I got it? Also, I water it ever 2-3 days and the humidity in the room varies from approx. 55-65 percent (there are a few other orchids in the room, so I keep a humidifier in there). It's hanging over my kitchen sink, which gives it a tiny bit more humidity. I also mist it every day. Is that good or bad? It gets approx. 700-1000 fc of light in front of a south window. Please let me know your thoughts as to where I've gone wrong and what I can do to remedy the prob. I would appreciate any advice.
Thanks in advance,
Vicki