I don't use chemicals......always found their smell unpleasant.
And other than a whiff when flushing due to open line to toilet we don't have foul odors. I find chemicals just a marketing hype
You stated "...lately i have been getting a foul odor from the toilet when we flush."
Odor only when you flush:
*Exhaust fan(s) running will pull odor up from tank when you flush (open line from toilet to tank)
*Toilet drain line to tank has build up of stuff (use a toilet wand on end of garden hose and blast line)
*Toilet pedestal is nasty (inside portion between toilet bowl and floor flange)---would need to remove toilet, take outside and blast away on it.