Does it smell fishy?
What brand are these lamp holders?
Could you swap a lamp holder and flex from another fitting that you know does not smell to the lounge temporarily and see what happens?
There may be arcing and burning if you had a loose connection in a rose or the switch, but I don't think the smell would be that obvious that quickly.
You could turn off the lights and re-check all your connections to make sure they are all secure, including connections made by the factory, ie inside lamp holders.
If they are, I would point the issue towards the lamp holders, especially if the problem goes away when you swap the lamp holders over.