The fuel pump is not holding pressure?

Hello, so your normal fuel pressure spec is 59psi +/-5psi. If it's not holding pressure after the key is off either the pump's check valve is stuck open allowing fuel to leak back into the tank, or a fuel injector is leaking fuel into a cylinder, in the case of an injector leaking that much fuel down you would notice a ton of white/blue smoke at start up or even worse the cylinder would hydro-lock because a liquid cannot be compressed. So, if you don't see any smoke at start up then its most likely something to do with the fuel pump itself or the fuel lines which you would be able to see. The Fuel Pressure regulator is built into the pump in this design so it's in the tank with the pump. I'll put the fuel pump operations service info up for you.
If you can block off the feed line from the pump at the fuel rail, and just turn the key On, so it primes the system, then monitor just the pressure coming from the pump, this way the fuel injectors are out of the equation. Then you can tell if the issue is in the tank. But you need to separate the rail and the pump to determine the exact cause of the issue.

Here is the Fuel Pump operations and service info also has a Fuel Pressure Leak Down diagnostic flow chart that I will post as well, just give me a minute.

This is the rest of the leak down flow chart for diagnosing the issue.

And you're sure it's a fuel pressure issue? Have you tested fuel pressure first thing before the first start of the day? Such as just seeing what happens to the fuel pressure after you turn the key to just the on position, not starting it. You should get a 2 second prime with the key On, and that should bring fuel pressure up to spec, and it should hold there.
But if the only hard starting time is in the morning during a cold start, then there are other possibilities. Since it looks like you need to T in a fuel pressure gauge on this system, I would have it set up the night before, so in the morning you can check your fuel pressure first at just Key On, see if it holds, then cranking.