Coolant Loss on 300TDI engine

Hope everyone is doing good. Please advise on coolant loss on this 300Tdi Engine. There is no coolant mix in the Engine oil and it does not misfire. P Gasket was replaced about 300 miles ago and there is no sign of coolant leak there. In the winter exhaust does spit out some water, soon as the engine warms up then it stops.
I tested the coolant leak with this coolant pressure tool on 20PSI then discovered coolant was leaking from 2 hoses, after tightening the jubilee clips it fixed the leak.
But it was still loosing some coolant about 50ml every 40-50 miles. When I went under the vehicle for inspection I discovered small amount of coolant runs below the gearbox. Which made me think it may be leaking somewhere from the back of the Engine.
With a endoscope help, I discovered that middle core plug (behind the Turbo) is badly rusted and noticed some coolant leak there. After removing th e Inlet manifold and turbo, I tested it again with coolant tester tool on 20PSI. Then one of the exhaust port from left to right number 5 started leaking too as in the picture. Does that mean cylinder head has a minor crack or advise otherwise please?

There is another one of those welsh plugs at the back of the motor - which would leak down onto the g box

The exhaust port seep could be just a tracking leak from a waterway through the head gasket to exhaust port but the only way to know is head off.
Can see other core plugs have been renewed and the heater transfer pipe has been replaced with copper tube.
All sign's that engine has spent time with just water in cooling system with no corrosion protection.

D1Nut said:

There is another one of those welsh plugs at the back of the motor - which would leak down onto the g box

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Just out of interest @D1Nut but where does the name "welsh plug" for what we call "core plug" come from. Cheers.

tottot said:

where does the name "welsh plug" for what we call "core plug" come from.

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Something to do with leeks?
I'll get me coat ------

tottot said:

The exhaust port seep could be just a tracking leak from a waterway through the head gasket to exhaust port but the only way to know is head off.
Can see other core plugs have been renewed and the heater transfer pipe has been replaced with copper tube.
All sign's that engine has spent time with just water in cooling system with no corrosion protection.

Click to expand...

Thanks for your reply, I have been trying to restore this vehicle from last 5 years gradually. From last year or so I am trying to fix things on my own as I have a garage and tools now. One of the core plug were replaced my myself without removing the manifold and turbo about 2 years ago. At the time maybe the middle core plug wasn't leaking but can't remember exactly. I made a
Copper pipe myself as the original one was badly crowded. I do not do lots of mileage on this maybe 1000 miles a year That's all. But I can remember exhaust were always spitting out some water on cold start. I am going to dismantle the Cylinder head and going to watch some instructions on YouTube and on the Manual. I will keep it posted here