The last 2 boat i've purchased have spent some time in FL, the current one, an 09 infusion spent about 8 months on the beach in Pensacola.
This is the 2nd boat that has developed vertical streaks down the hull. On my 04 N20 I attributed it to oxidation, but on a 1.5 year old infusion? I wax the boat 3-4 times a year.
I've come to the conclusion that it has something to do with both boats coming from FL.. any ideas? I've never had this issuue on previous boats nor seen it on any other boats here.

Maybe those boats just don't like being sailed by you.

Try FSR and wipe it down with that before your next "waxing" It'll strip most anything off. Make sure you do it in small sections and rinse in a minute or less. If you wipe it on and leave it, it'll attack the gelcoat.

What kind of vertical streaks? Black streaks or dull finish streaks?

mine gets the black streaks too.

Its called

Rain water.

probably acid rain

i have not really seen that in central Florida (i would GUESS we get less acid rain here with the gulf cleaning out the precip. N Florida would get all the pollution from the entire US. esp refining along the gulf coast)

If it is rust stains, the salt water here can even cause some stainless bits to rust.

I replace my standing rigging every two years and my pigtail every year.

Black vertical streaks, some darker than others.
After cleaning when it does rain they come back right away, but like I said this never happened on my old boats and the rain water in NE is from only the finest springs in Maine
I compounded the crap out of my 20 and waxed it and it looked great sailing in in the Steeplechase and Tybee, but I sold it the day after so I don't know how it looks now.

Dirty rain and/or mildew. My boats get it very very fast in SC. I usually keep a cover on them when prevents it but every now and then I leave the cover off and just one rain causes the streaks. If the boat is relatively clean, I don't bother washing it, I just wax it and the solvents in the wax will remove the streaks.

The roofs on the houses around here are run amuck with it (you can see it particularly on the roofs that are not black). Zinc (washing off roof fittings) will eradicate the black streaks on the roof shingles which makes me think it's a mildew thing.

I get those streaks here in MO too. I get them in FL. It doesn't matter where I keep it. However if you keep it covered as I do now you don't have the problem. I cover my whole boat after each use. Some boats around here it's hard to see the gelcoat through the black streaks.