Salt Mixing Problems

[Potatohead]

I'm going to assume that 3.3 is meq/L and not dkh?

I don't have much to say as to why it may be happening, it sounds like you are mixing in room temp water which is good... If you have any calcium chloride and epsom salt and/or mag chloride you can correct what you have but I hear you that it would be good to be better out of the gate. I have been using the Seachem salt for a little bit now and never seen this myself. With zero TDS I wouldn't imagine it is your water, but for experimentation maybe try mixing a small batch with water right out of the tap and see what happens?