Another cold start problem!

Is a 2004 2.0ltr tdi.

A while back I had cold start problems which turned out to be the battery. Got this changed and everything was fine.

Over the last 5 days or so I have had issues with the car struggling to start in the mornings. I turn the key and he tries to start but takes a while. It seemed worse after I left it over the weekend.
This morning actually took 2 attempts to get it going.

I had it scanned a few months back and it did say that glow plug number 4 was faulty. Could this be the reason? Then again it is not really cold at the moment.

The other thing I thought of was the starter motor but if it was this would it not struggle at other times in the day and not just he morning.

I do get some white smell smoke come out of the exhaust in the morning but I have not noticed any coolant loss.

What do you guys think?

Thanks

Any ideas guys?

Really. I thought glow plugs did not come into effect until it was really cold?

Am I right about the glow plugs?