I have two toilets, both use the same vent pipe to the roof. And are on a septic system. One of them flushes fine, the other is a bit slow to flush and burbles and burps. Could there be an obstruction in the vent that only impacts one of the toilets? Thanks!

Your burping toilet has a partial clog in the main line that must be snaked out. You have two options.
1-pull the toilet and snake from there. **OR**
2- snake from that bathrooms lavatory roof vent. If you snake from the roof put out enough snake to reach the base and 15 feet more. Good luck, Tom