Hi,
Thanks for the further replies.
Let me clarify my process.
1) I use stainless steel reels (Hewes) in a metal tank with a plastic top. I soak all this in warm tap water once I've finished one film to clean it.
2) My XTOL is mixed with deionised water which I buy in a bottle. I mixed at room temperature (usually around 22C), and I did it by putting 4L deionised water into a 5L bottle, pouring in the XTOL A, and then inverting the bottle until I couldn't see particles, then the same for XTOL B, then the top up with more deionised water.
3) I develop at 1+1 dilution, with more deionised water.
4) I keep a pre-mixed stop bath, made with deionised water. I chuck this when the colour changes.
5) I keep a pre-mixed fixer, made with deionised water. I chuck this every so often.
6) I wash by leaving the tank under running tap water for 10 minutes
7) I do the final rinse/wash with a photoflo solution, made with deionised, and I keep this as a "working solution" for 4 or 5 films.
8) I hang in the shower cubicle, which is largely undisturbed
All of this works fine with anything except XTOL (and now Instant Mytol)
I'm trying an Ilford wash cycle right now, to see if this helps with Instant Mytol.