Bad fermentation from washed yeast

I started this thread yesterday in the "general" catagory, but got almost nothing in response, so I thought I'd try it here.
I have a batch of washed Cry Havoc that I used to make two AG batches of Pale Ale.
The first batch I made with Marris Otter, I used yeast nutrient in the starter, and had a target FG of 1.017. It finished at 1.026 !
The other batch, the exact same ale, only with 2-Row pale malt (and I forgot the yeast nutrient in the starter), also had a target FG of 1.017, and it wound up finishing at 1.020. Granted, that's only 3 points off, but I've never finished THIS far off before, and I'm equally amazed at the discrepancy between the two FG's.
My OG's were only one and two points off.
Does anyone have ANY idea how/why this happened ???

I don't know, but I have read that sometimes washing yeast can collect less attenuating yeast. I have read that it is a good idea to use a seocndary fermentation vessel and collect from there because you have dumped the less attenuating yeasts. Take this with a grain of salt because I am just researching yeast ranching and haven't actually started yet.

I've washed yeast once before, a Belgian Ale, and had great results. I used it from the fermenter, following the instructions, just like I did this time.
I had intended to wash this round of yeast, too, but now I'm a bit reluctant.

Did you aerate? Or put 02 to the wort, washed yeast needs it.

David

I aerated it just like I do every batch that I make, new yeast or washed.

Boerderij_Kabouter said:

I don't know, but I have read that sometimes washing yeast can collect less attenuating yeast. I have read that it is a good idea to use a seocndary fermentation vessel and collect from there because you have dumped the less attenuating yeasts. Take this with a grain of salt because I am just researching yeast ranching and haven't actually started yet.

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actually, this is not correct.

you wash primary yeast to get the largest yeast colony. secondary washing is bad for two reasons: far less yeast, and its the less FLOCCULENT yeast (meaning it falls out of suspension slower than the yeast that already fell in primary).