I'm experiencing a similar problem myself and I haven't got the solution but wanted to offer some thoughts. I used the Tetenal E6 kit a few years ago and had no problems with processing. This year I purchased another Tetenal E6 kit and started by processing some expired Velvia 100F in 35mm. I had shot a roll of this earlier this year and rated it at EI 64 to allow for the expiry but it seemed underexposed with a lot of magenta in the shadows. So with the next roll I exposed it at EI50 and ended up with a roll mostly consisting of overexposed shots, but with a few that were OK.
My first thoughts were that I had overexposed in camera but then I came across a thread (think it was on apug/photrio) which pointed out some issues with the Tetenal instructions, which might lead to overdevelopment.
First the Tetenal instructions (
https://www.freestylephoto.biz/pdf/product_pdfs/tetenal/TetenalE6_Instructions.pdf) are ambigous as to whether their recommended times refer to rotary processing or to agitation.
On page 4 that "COLORTEC© E-6 3-BATH is for the development of E-6 compatible colour slide films in
rotary discard processors".
On page 5 they give times of 6'15" for first developer and 6'00" for colour developer.
Later on page 5 they say "Agitation Step 1 (FD), 3 (CD), 5 (BX): constantly during first 15 secs, then once every 15 secs.". This is confusing because you cannot have intermittent agitation in the middle of a rotary proces (well, you can if the motor doesn't work and you have to rotate manually, like my Jobo, but that's another story). This sentence gives some doubt about whether the times given are for rotation or agitation.
However Jobo publish their own recommendations for E6 processing times here -
http://www.jobo-usa.com/images/manuals/introduction_to_processing.pdf
The relevant extract is:
Recommended Process Times for Kodak E-6 and Tetenal E-6:
Rotation Speed (with reversing directions) 'P'/75 for 1500 and 2500 tanks, '4'/50 for 3000 drums Temperature 38°C (100°F)
1. Pre-Warm 5:00
2. First Developer 6:30 (All Fuji films only: use 7:30)
3. Rinse 2:00 (4x 0:30) 4. Reversal Bath 2:00
5. Color Developer 4:00
6. Conditioner 2:00 (or Pre-Bleach)
7. Bleach 6:00
8. Fixer 4:00
9. Rinse 5:00 (10x 0:30)
10. Stabilizer 1:00 (or Final Rinse) (Off processor at room temperature.)
11. Dry As Needed
Note that the recommended First Developer time (step 2) is slightly longer than the Tetenal time for Kodak films and much longer for Fuji films. The Colour Developer time, however, is much shorter.
So I am tempted to try processing my next E6 roll using the Jobo times to see how they turn out. I'm going to eliminate the expired film from the equation, because in my case I only have one roll of expired film left and quite a lot of fresh Provia and Velvia, including some 4*5 Velvia which I can't afford to get wrong. Im going to shoot a part roll of Agfa Precisa / CT100 but also do tests at varying exposure speeds.
If the shots taken at box speed look right then there are no further adjustments needed and I can go ahead and shoot the rest of the film.
If the box speed shot looks too light then I'll look for one of the shots exposed at less than box speed to see how they turn out - if, say an EI64 shot is OK then I can either shoot the remaining film at +1/3rd stop or try again with a shorter first developer time.
Obviously the reverse method applies if the box speed shot looks too dark.
Note that I said I would, if necessary, change the
first developer time rather than the colour developer. I say this because the Tetenal instructions, on page 6, say that if slides are too light this can be caused by:
- Over-exposure
- Temperature of the first developer too high
- First developing time too long
- Agitation at the first developing too intensive
- Contamination of the first developer with bleach-fixing bath
It seems that the first developer affects density whilst the colour developer effects, well, colour.
However, I still have some doubt because the Jobo times will lead to me increasing the first developer times, compared to the Tetenal time I used which already gave me slides too light.
I realise my response hasn't really answered the question, but I thought it was important to note that something more than adjusting for the expiry of the film may be needed.