anyone know why my dogs coat is all of a sudden really dandruffy and dull looking, and any ideas to make it nice again.

Hi there pugggg
Dandruff can be caused by quite a few things.Diet can affect the coat and it could be dry skin rather than dandruff have a look at what you are feeding and ask your vet if she needs it changed ie might need added vitamins etc. Is your dogs health ok is he behaving as he/she usually does?
Modern living and central heating can also affect the skin and dry it out causing flaky skin .Try using a good dog shampoo one for dry skin I use  Tea tree shampoo on my dog as she tends to get a bit scurfy,this is usually when her coat starts to get a bit longer ( I clip her every 8 wks )
Be carefull although when trying a new shampoo in case there is a reaction and makes the problem worse perhaps do a wee patch test first.
If you are worried  call your vet and ask for advice.

Have you changed the food at all.  Coat condition is a good indication of what is going on inside.

Shampoo wise - Doreen Paige do a great range and I can recommend their Dermadate (sp ??) shampoo.  I've used it and it leaves the coat sparkling and settles any skin irritation.

Vicky

Some dogs get quite scurfy when they are moulting.  Are they loosing their puppy coats?  I can't remember what age you said they were.