Possible fuel filter issue

[SectorOMEGA]

Hello, Im trying to figure out a possible issue with fuel filter and loss of fuel pressure. I have code p2291 and just doing some visual checks when I saw that I have a leak from the fuel filter cap, specifically at the button that is used as pump(correct me if Im wrong about the pump). Is this normal or it should be dry.

[GiveMeABreak]

You need to check the unions are on tight as there shouldn't be any leaks. Second make sure it's not from the water bleed screw (2):

Failing that it may need replacing. P2297 does include the Fuel Filter as a Suspect for this fault code:

Fault Code:	P2291
Description of Fault:	Starting monitoring: Pressure increase in the injection rail too slow when starting' Fuel injection common rail pressure increase time too long (Threshold at 700 ms when the coolant temperature is 5°C)
Conditions for Fault to clear:	When starting a warm engine
Downgrade Modes whilst Fault is active:	-
Symptoms:	Starting problem Fluid leak/smells (diesel fuel, oil, etc.) Smoke from the exhaust Slightly higher fuel consumption Jerking/stalling Lack of power Engine stop downgraded
Suspect Areas:	Air leak on the fuel filter Clogging of the fuel filter Running out of fuel Leak in fuel circuit (low pressure) Fuel high pressure flow regulator High pressure fuel pump Leak on the high pressure fuel pipes Leak on the fuel high pressure common injection rail Fuel injectors Electrical harnesses Connectors

[SectorOMEGA]

Brilliant as usual Marc! Thank you so much! Water Bleed was on the wrong side, fixed thanks to you, but now I have deeper problems and honestly don't know where to start.
As of now I have B1811 - Fault On The Diesel Fuel Additive Pump and I have checked the reservoir its type BVH2, it has fluid in it but still the error remains. Im trying to do a search if the reservoir is all in one pump and tank and from where to start troubleshooting Also the car is in limp mode and the diagnostic(TopDon 900bt) shows 100% DPF and around 10mbar on idle.