pilsner issue?

Hi,
I've done about 6 all grain brews, and the 4 that I did without pilsner malt turned out great. I brewed Jamil's hefeweizen and NB's Lefse Blonde. They both came out not so good and had the same off flavor. I use proper sanitation practices, temperature control and pitching rates. My boil is the thing that I'm wondering about. I do a rolling boil but it's not super vigorous. It's uncovered for 90 minutes. The final turnout of these beers is very frustrating. Does anybody have any suggestions?

Can you describe the off-flavor?

Pilsner malt is more prone to produce DMS which might not be driven off if your boil isn't vigorous enough or if you don't chill fast enough. DMS is the cooked corn smell/flavor.

It's a little hard to describe. It's kind of like a medicine off flavor, but the smell is something that I would guess to be DMS. I've read that medicine taste could be from phenols, but I sanitize thoroughly and the batches in between these two have turned out great. I guess the only thing that I can narrow it down to is DMS, since these are the only two brews that I've made with pilsner malt and they have the same taste.

You may also be under pitching the yeast or fermenting a little warm. Both of those styles usually use a Belgian style yeast and a lot of Belgian yeasts are cultivated to give a nice spicy banana/clove balance when used properly. If it is underpitched or somehow stressed too much you can end up with to many phenols from the yeast and can give you that band aid flavor.

For Jamil's hefeweizen recipe I made, I pitched a 1.5L starter and fermented at 62F, monitoring it by a digital temperature controller and thermostopper. This is the confusing part.