Sometimes when I mix this up it gets a milky whit cloudiness to it. anyone know why?
I believe it’s reacting with hard water, particularly magnesium or iron. There is a Brewing Network show with someone from 5 Star. http://thebrewingnetwork.com/shows/469
Yeah I get this too. When I mix it up for a spray bottle I only use distilled water so I’ll know any cloudiness isn’t from my hard water.
I’ve had this same cloudiness clear up after a couple hours of sitting out. Sometimes my starsan mix will cloud up the second its mixed up to use.
I’ve been running into this problem lately- even though the water is RO.
But the starsan is about 6 years old and has cracked caps. Also the starsan has grown darker instead of the clear syrup it once was.
Barely any left so I’m just discarding any solution that’s left after a brew session.
My experience went the other way. I’ve noticed that my water gets cloudy more often now that I’ve used up my old bottle with the cracked cap (did you drop yours too?) and moved to a new bottle.
This is the reason.
Use RO water when mixing your star San.
I contacted 5-star to ask them what to do when my cap broke (it was worse than a crack). They sent me a half dozen new ones, never asked for anything in return. Now I save the caps from the old bottles so I always have a few around just in case.
Caps on 1 gallon Star San do not crack 
I think the cracks come from screwing the caps on too tight for the strength of the plastic, and possibly the starsan might weaken the cap some.
Just checked some solution made a couple days ago. Crystal clear but I have been discarding quite a bit instead of reusing it. Honestly, starsan seems to work as well fresh or when it is murky or has bugs floating in the solution. Wonderful stuff.
I replaced mine with a soda bottle cap.
I should have thought of that - I just tried it, and while it’s a rough fit it seems to work well enough.