Don't under estimate variance! It tends to be amplified on the move up. I don't know why...
Maybe, in part due to...
Scared money.
When you double your buy-in it is possible even at $3-6. If you are a little intimidated it shows. You must be willing to take risks at least as much at the higher BI. Opponents tend to get more aggressive as you move up the ladder too (even at micros) so you'll get a double whammy. You need to be more aware of who has cards and who is likely to be shoveling money. Playing 4 tables with no Poker Tracker doesn't allow this level of awareness.
1 more question, why turbos? As a profitable player the fast structure works against you.
I get a sense that you are pressing, trying to 4 table in order to build your BR more rapidly while technically staying within guidelines:joyman: . (Kudos on the BR management BTW) In the OP I got that feeling you are trying to dictate the absolute worst case expectation, when in reality the "poker gods" may have other ideas, like 8th,6th, 4th,4th. Slow down! Try some non-turbos $5.50, less tables . Maybe even take a shot at a $10 and 1 table. Sometimes multi-tabling will serve to make a profitable player into a break-even or losing player. I find 2 tables is a good balance for me, I can pay attention, not get too bored and still cruise the forums.
good luck,
goldog