I always order flavourless PG with nicotine (28mg strength) in 30mL bottles from
Evapers,
BBB. And plain PG/plain VG from
Happy Vaper.
Evapers has delivered a remarkably consistent & really good flavourless PG with nic to me, and they're as speedy with the shipping as Jack is. So yeah, I recommend them. It's a bit difficult to find on their site the way it's set up, here's the link:
evapers.com/tryout/index.php?route=product/product&product_id=77
Just choose Flavourless in the fields, and the strength you'd like. 28mg is their highest.
But yeah....
rust coloured?

That is
not normal. I'd advise getting rid of that asap.
Switched is right - the clearer it is, the fresher it is. If it has a slightly yellowish tint to it, that's ok - just means it's had a bit of oxidization. Even the clearest bottle will turn to that light tint naturally, over the course of your using it. But rust coloured...at best, it's old & poor & not going to vape particularly well. At worst...I'm not sure

but best to get some fresh stuff asap.