So I discussed extensively with a local laser company and they agree that it is the tube that is toast - looking especially at the spot size as @jkwilborn mentioned.
So I bought a new 50W tube and am in the process of installing it. The problem is that it is much longer than the old tube - some 20cm longer.
It is a Joy brand tube, the Chinese sticker is rated at 60W but the local vendor has a certified test facility where they test the tubes, for your interest I have attached the ratings card below:
They tested the tube at 12mA and it produced the output listed above that in watts at the specified duty cycle (I assume that is the duty cycle). I assume that is the percentage that I should set in Ruida as the maximum percentage. Will keep the ammeter in the loop just in case.