What causes a few flower petals to brown?

[Paul Mc]

I have two orchids (one Phal and one Brassia) where a few of the petals have turned brown (almost as if they are dried). The petals are only the bottom two in the back of the flower (I know, I should really learn the technical term for this given my obsession, lol...).

I think I know the cause but I'd like to get your feedback to see if I'm possibly on track or not.

The neighbors on both sides of our house cut down their enormous trees allowing more sunlight in from the east and the west. Plus, I recently repotted my Phal in fresh medium and have been less than diligent about ensuring it has enough water this year.

My thoughts are that for the Phal it has been a combination of more light (especially the heat from this time of year) and lack of water due to the fresh medium, and the Brassia may be a lack of needed water (only watering once a week thus far but intend to up it as for me they appear to be water lovers) and from the intensity of the sun.

Do you think I may be on the right path?