Hey, I need some help. Here's whats going on. Two story house with toilets on main level and second floor. Both toilets don't flush or flush very slowly. I thought it was the main line, so I removed the main clean out plug and it was clear. So I left the cap off and flushed both toilets and they drained perfectly. So now I'm thinking it's a clogged vent. I also ran a snake down the main line 40ft and didn't hit anything. If I put the cap back on, the toilets don't flush again.