Please help a newbie!

I've been stalking these forums for a while and just recently decided to start CG, since I seemed to be a textbook case: really frizzy hair that couldn't decide whether it wanted to be wavy or curly and that got super oily less than 24 hours after shampooing.

I'm in week three now, and having some odd issues. The biggest is that my hair seems to have reversed itself - my roots look good, and are if anything overdry. But my ends are super stringy and greasy-looking. This is bizarre to me. Is it possible to get product buildup on just the ends? I've been keeping it EXTREMELY simple since I'm just starting out - just doing a co-wash with Suave, no additional products or rinses.

I think I may have really hard water, but it's hard to find out - I currently live in Okinawa, Japan. I've vaguely heard that there's a lot of coral-related calcium in the water. Because of the Japan thing, too, it's hard for me to get my hands on products whose ingredients I can understand. :P I got the conditioner when I was in the States for Christmas.

I've been considering doing one wash with a sulfate shampoo because it's getting bad. I've got some Nizoral on hand (it's meant for dandruff, but I used it about a year ago for a skin issue instead). It's got SLS, but only as the second-to-last ingredient, and no cones. Think it would be all right?

Thanks, everyone!