Ryuka
Glad you have joined us here at the OB
Your Phal seems very healthy ..
You might want to take a look at the condition of the root system .. It looks like it's in a mixed medium
If the medium has broken down .. where it begins to resemble 'dirt' and is no longer chunky ... you might want to consider repotting ..
My personal perference is getting a clear slotted container - it allows you to view your roots at any time ..
When buds fall off , it can be caused by bud blast - which is due to some environmental change .. - in lighting, temperature, humidity or watering for example ...
The flowers will wilt over time and naturally fall off .. are you talking about a premature wilting?
I would leave the leaf .. the plant will abort it on it's own .. besides I don't see any sign of disease .. ( it's just a little beat up)