I was in the same rut, shot HORRIBLE first week of this league, but had been off track the last couple weeks of summer.
Took two weeks off (one for Holiday), and returned. Started out like the rut - open spare - open. Then found something to salvage a small 200 for game one. Game two - spare - spare - sheet. Game three - solid 2teen game.
Other team not so happy since handicap league, but we all have fun in that league.
I hope you will take the time off to re-set. Maybe go throw a couple games, video yourself on your cell phone and see if you can diagnose the issue. It may just be mental.
It could be as simple as: Stop thinking, bowl and have a good time with your friends on the team. I was in a huge slump two years ago mid way through the season, and I was talking to one of my teammates about what goes through your mind on the approach. At the time of my slump it was "don't open". He told me to re-direct my thoughts to "I am gonna strike". It was like PED's for my game after that!