Ralph,
After cleaning one of my Waterridge toilets the other day, I noticed a rough surface towards the front of the bowl. There is no stain, but it appears to be a mineral buildup there.
I visited the local OSH today. It was with some difficulty I located the two Whink products they carry. One was the two tablet package you mentioned, which is what Whink recommends for colored toilets. It says it's a lime scale and rust stain remover. It contains a sodium sulfite as its main active ingredient. You're supposed to add one tab per month to keep the bowl clean.
The other product was labeled only as a rust stain remover, and for white bowls only. This one has hydrofluoric acid in it, and recommends near immediate flushing after application. I assume it's because hydrofluoric acid is what is used to etch glass (as in frosted glass designs). Is this the product you used?
I notice on Whink's web site they also list a liquid product that is recommended for both lime scale and rust removal. It contains a complicated organic acid, nothing simple like HCl or HFl. But I didn't see that product at OSH.
In any case, I didn't buy any Whink product today at OSH. I have some Lime-Away stashed away from years back, as well as some phosphoric acid based lime remover that I'll try first. And of course I have a Pumie too, just in case.