Premade 5v5, Normal - Getting weird matchups (1 win, 7 losses)

Hello fellow LoL friends,

Some of my friends and I have been playing as a premade group of 5 in normal games (a mix of blind and draft). 3 of the team members were once silver level players, one used to be bronze, and one is a noob (me - level 20 now).

However, we've been being placed against people much better than us (to the extent that we've lost 7 out of 8 games). It's kind of disheartening. Compare this to my solo games (in 5 solo, normal games, I'm 60% win rate by myself) and games where I've played with just two of my friends (where out of 5 games, we've won 4). This feels like such a stark difference and while it's possible to be completely by chance, it feels crappy and it causing one of my friends to not want to play anymore.

Do you guys have any suggestions to make our premade 5 team more fair/fun? Is one game mode better or worse than others?

Thanks in advance for your help and insight!