Most marinas will restrict wiping down the bottom since the antifouling agents (copper, tin, etc) build up on the bottom of the bay over time. Apparently, if you dive you can see where the bottom is pretty void of sea life compared to other nearby areas in older marinas. Somewhere down the road the areas where this has happened will have to be "cleaned up". Just as the places where oil and other byproducts were dumped are now Superfund sites. I wouldn't want to be the marina owner when that regulation went into effect.
We see the same type of environmental regulation on boatyards now. For almost 20 years now the boatyards have to capture all the water from pressure washing bottoms and recycle the water. The sediment has to periodically be shoveled into drums and placed in a HazMat landfill. You've probably noticed that boatyards now require tarping around boats prior to bottom paint sanding so the toxicity doesn't spread.
A couple of things help reduce the growth. Regular use seems to keep the growth down. Dark tends to limit growth. Under cover is better than in the open and inside a boathouse with the curtain drawn seems to be the Gold Standard. Areas around the waterline do tend to be messy, so running the brush around that area when anchored out somewhere probably won't impact the bottom there as much as it would in your slip where the toxins would fall in the exact same place each time. Taking your diver out somewhere to wipe down the bottom every 6 months might work for this also if you find that your marina seems to be warm enough to grow more than normal.
For recoating the bottom paint I'm a proponent of waiting until it needs it. That is I have mine looked at every 6-8 months when the diver does the zincs. If it is just building some slime from not having been used enough, I use that as an excuse to go for a ride. (bottom paint is $200.00 a gallon, diesel is $4.50) When the diver reports seeing the next color down, then I know it's time to schedule a paint job. Sometimes it happens in the spring, sometimes in the fall. Yes, I alternate bottom paint color every 3rd time or so. I sometimes go 3 years between coats. Of course the disclaimer is I use sloughing paint on a slow (7 knot) boat. If you're on top of the water doing 30 knots with a hard paint your experience will vary.
I'm in Edmonds marina for the weekend and the water outside is 50.2 degrees right now. (tell me again how cold that 70 degree water is......
Our normal water temperatures in the Sound run between 50 and 55 degrees most of the time unless you are in a large shallow area that gets some solar heat.
Your zincs are a very individual item. Each boat has it's own amount of electrical leakage and who you moor next to can be dynamite. Certain marinas have electrical leakage into the water which will eat your zincs quickly also. If you are in a new to you marina I would pay close attention to zinc usage until you get a good feel for how quickly they deteriorate. Some folks go thru pretty big zincs in 3 months while others last 9 months or maybe more. In my marina, at my slip and my boat I get 7-8 months on my setup. Others in the same marina get significantly less. You are overdue to check yours if they haven't been seen since Sept. (in my opinion)
Not staying on top of the zinc issue will start typically to eat at your prop first. Props are a very expensive way to control electrolysis. Zincs seem expensive until you buy a prop at $1200.00 to $1800.00.
That's my experience in the Puget Sound since 1981. Yours may vary.