Has anyone noticed Great Tits with tumours or growths?

Hi - this is my first post and I've unsuccessfully tried to search the forums for anything else related to this - so apologies if it's been covered elsewhere! 

Over the last month or so, I've noticed a Great Tit on the peanut feeders in our garden and (without being able to get close enough to see exactly) I've noticed that it appeared to have a red growth of some kind on the side of it's face.  I've never been able to see it exactly, because by the time I get the binoculars it has always flown away!  It seems to be flying and feeding as normal.   I've only ever seen the one tit with the growth, so just put it down to maybe a birth defect or something in that particular tit.

However, now I'm a bit worried.  Today I came across a freshly dead great tit in the garden - full sized, not looking scraggy or underfed or anything, but with very large growths under the skin all around it's beak and throat.  The worrying thing is that it wasn't the same tit I've been seeing, as the growths weren't red at all - they are all under the skin.

Is this some kind of new disease that I can do anything about, like the trich..(can't spell it!) that the finches get (we had that last year and had to take all the feeders away for weeks - and now I'm scrupulous about hygiene on the feeders).  Or is it the same disease, maybe?   All of the other birds that I see every day on the feeders (we have lots of goldfinches, greenfinches, great tits, blue tits and chaffinches mainly) all look ok, but I'm really worried that it's something contagious.

The tit was very freshly dead - if it would help with identifying it, I can get it out of the bin and send a photo of it?

Again, apologies if this has already been covered, and for my first post being a bit grim - but it has got me worried!  Hopefully someone more knowledgeable than me can shed some light for me.