Phalaenopsis leaves yellowing/browning and bumpy

[Jinglebells0518]

Hi guys! I just bought 4 new grocery store phalaenopsis' and they are in full bloom so I am waiting to repot. But a few of them have some dying leaves and if I removed all of the yellowing/partially yellowing leaves a few of the plants would only have 2 leaves left and no signs of new growth. Is this normal as they get to the end of their bloom period? The leaves look weird so I just want to make sure there is no signs of disease so I have attached some pictures.

As an additional question, I will be repotting these orchids once the blooms drop so what is the best potting mix to use for phalaenopsis. I have a prior orchid in a better-gro mix that is pretty coarse and I seem to have to water 2 times a week or so because the coarse mix dries super fast but then I get worried I'm overwatering. Is this the right kind of mix? Should I get something with more sphagnum? What do the pros out there suggest? I'm considering mixing my own since I now own 6 orchids and the pre mixed bags are pretty small and can be pricey.

Thanks for all the advice. I wish I had an orchid expert to go to because I'm never sure if the plants need more water, how to get new leaf growth, when to repot and with what, how I tell if they are healthy, etc.