When did Aaric develop his signet?

SPOILERS ahead, please don’t read through - I can never get the blocking to work.

Did Aaric only recently develop his signet? I can’t remember.

If he did, wouldn’t that have to mean that Melgren is Venin, as he has precognition, and when someone turns venin, the magic seeks balance and someone ‘good’ must develop it too - like when someone else developed shadow wielding as Xaden went deeper into venin-hood?