Hello all,
I have quite a peculiar plumbing issue come up that I am doing my best to solve while waiting to hear back from a plumber, hopefully to avoid having them come out all together. But I am stumped for what could be the issue.

My wife and I moved into an older (1950s) home in East Memphis this past March with the following details:
- 1.5 bathrooms
- The half-bath was added on later in the "master" bedroom. It is very close to the original bathroom, almost certainly tied into it. Only a sink and toilet.
- Slab foundation, no crawlspace
- Main sewer line goes to the street, no septic tank
- 1 story house, hot water tank on the main floor, not in the attic
- The plumbing inspection in March came back clean, no issues.

A couple of months ago, both toilet stopped up at almost the same time, later in the evening. After much plunging, to no avail, my wife and I quit and settled on calling a plumber in the morning. No evidence of the shower/sinks backing up, although we did not shower that evening. There was some evidence of gurgling in the toilets when we ran the shower before the toilets started to back up however.
Next morning, toilets flushed fine, no issues.

Now, a couple of months later, basically the same issue has arose. Both toilets stopped working at almost the exact same time. One "flushes" but very weakly. The water will basically just slowly drain. The other's bowl almost fills entirely up until it slowly drains too. There was also some gurgling when we ran the shower before the toilets started to not drain.
This time, we have ran the shower twice, and the sinks several times, with no backing up whatsoever. Only the toilets struggle to flush.

Things I've tried:
- 6' snake in both toilets, went as far as it could go, nothing.
- 20' snake in both toilets went about 16' and wouldn't go further. I'm not sure if that's just because it hit a tee or something and being a skinny hand snake it wasn't powerful enough to push around it.
- Plunger in both toilets drains the bowls in just a few pumps. The water isn't resisting the plunger, just the flush.

Was going to check the vent pipe on the roof since that *may* be an issue, but it started raining heavily before I could go get a ladder so I cannot get up there now.
Does anyone have any thoughts before this plumber comes? Anything to help save a buck or two would be greatly appreciated!

Your main line is clogged and needs something bigger/longer than the augers you are using.