My own personal experience with bulk chemicals is that I have no personal experience with bulk chemicals
I wanted to go to them for $$$ reasons but my LFS owner highly recommended I don't for the exact reason you may be running into now. He recommended I use either the Tropic Marin of Fauna Marin systems. There is no way I can say the bulk chemicals are what caused your problems, but logically what else did you change that could impact your tank this dramatically?
If you're using a quality brand of salt, it should test pretty well for the big three parameters. Just buy doing frequent large water changes hopefully that can dilute the contaminants and maintain your values. I'd suggest you get back to dosing with commercial products as soon as possible though to promote some stability.
The good thing about this hobby is that once you get knocked down, fellow reefers are usually happy to help you out with frags, etc. to get you back on your feet.
Good luck!