I have the same 6 cavity mold. :-) It is one of my favorites to cast with and gives me exceptional quality bullets. I think you may not have removed all the oil out of the mold when you first cleaned it. I really scrub my molds, using lighter fluid or alcohol. I also take a soft bristle brush like a tooth brush and scrub them with dishwasher detergent and hot water from our Insta-hot faucet.
I occasionally see a few wrinkled bullets after putting bullet lube on the mold alignment pins in an effort to lubricate them as described in the Lee instructions. If you put too much bullet lube on the pins, a bit of it may migrate to one or more cavities. This cause of wrinkling usually goes away fairly quickly. Remember, when you get the molds up to temperature, just a TINY bit of bullet lube will do the necessary lubrication of the alignment pins.
You also may want to try adding a little tin to your mixture. I buy 95%Tin/5%Antimony solder at a local hardware store in 1 pound rolls. It is expensive, but it wouldn't take much to give it a try.
