Yellow leaf and mealy bugs?

[Joyorchid]

I bought this little phal in spike from a reputable orchid nursery near my home a few weeks ago. I placed it under a skylight in our kitchen and water it twice a week. It is potted in fir bark, perlite and charcoal. I fertilize weekly with a 13-8-9 solution that has calcium and magnesium. I found mealies on it last week and sprayed with a alcohol and soap mixture. Have not seen mealies since but today I noticed the leaf is yellow. BTW, the crown and roots look good.