I've opened a blister and I found a capsule that is discoloured, a darker colour. Is that normal?Updated a year ago

Yes that's normal!  Because we have ultra clean formulations, we don't use stabilizers that prevent discoloration when capsules are exposed to heat or humidity.

Discoloration means it has absorbed moisture from the air (common with choline-containing supplements).  If you want to prevent that from happening, store them in the fridge.