OK, a few more ideas :
You mentioned distilled water a couple of times - but are all your tanks mixed using distilled or RO water?
I don't know if it will have any effect, and I'm not certain which de-ox/de-smut you're using, but if my memory is correct, the de-ox/de-smut we get here from Caswell UK is used at ambient, not heated?
Is the Grey the first dye you've tried? or are others OK and just Grey bad? We've never used the Grey dye, but, for example, Black is possibly one of the most demanding colours, and Red maybe the easiest - so if you've got any Red or similar, it might be worth trying?
Have you got
enough cathode area?
Is this the first run(s) you've done in this ano tank? - if so, things may get better ..... to run properly, the ano tank needs
a certain amount of aluminium
Dave