1 year back, one of my very new rigs was taking 450 Watts on the wall.
Now I've just checked and it's consuming 600 Watts for the very same hash rate.
Does the efficiency go down this much of the hardware?

your rig is possibly becoming wiser with time and does something productive for itself on your expense
Dust or PSU, you need to blow it out w/ air
It should not happen: the worst PSU I had, went from 88% efficiency down to 78% in a year and bit.
You are talking about a huge drop: something like a PSU at 90% efficiency going down to 60% efficiency.
Yes, that's why I'm curious. It'd have been fine if it was 50 Watts increase in power, but jumping from 450 Watts to 600 Watts is really ridiculous, specially for a new bronze Corsair power supply.
I'm going to open up my PSU, GPU's, whole system and suck some dust through the stuff through a light vacuum cleaner. Let's see what happens.