Phal help for a friend - sunburn?

[TwoStems]

I'm posting this for a friend of mine who's got a few orchids. All of them are healthy with the exception of one Phal. She bought it in bloom/bud and it has gone through it's cycle. She repotted it on s/h about 3 weeks ago and has put it in a slightly shadier spot since repotting it. The damage to leaves was before repotting it. She isn't seeing any new growth and lost the bottom most leaf recently. She's wondering if this damage is in fact sunburn or something else and if there's anything she isn't doing that she should be, or visa versa. We've found conflicting explanations for the damage. She has city water and is planning to try bottled spring water to see if it will help. She fertilizes "weakly-weekly". She has a baby Catt in the same location as this plant and it hasn't had any problems, and several plants in the former location of the Phal that are also doing just fine. Any ideas?