Miltoniopsis-brown edges on blooms
 

Why do the edges of my white Miltoniopsis blooms turn brown when they open?

It could be getting burned.....chemical or sunlight. Cut back a little on fertilizer and move plant to a different location. One of those might do the trick. If you are already fertilizing weak, it might just be the sun.

In my case it was lack of water combind with a lower humidity level.

I agree with Lagoon.....Miltoniopsis enjoy moisture both in the mix and the atmosphere. A dry and warm house is definitely not the preferred situation. My plants have been blooming all summer which is quite odd, but they don't hold up as well in the warmer weather.

Yes I also agree with Gloria.