It can happen. I've struggled some in the 3rd game of our mens league, but im not the only one. To me thst says the breakdown/transition were seeing is a little odd.
Last night 3 of us on same pair with 220 averages, 3 different styles. True cranker, true old school stroker, and me as a tweener in the middle.

First 2 games we were 470s, 440s, 490s. Last game the high between us was a 186, none of us could figure it out and all of us were playing a different part of the lane

Yeah, it's hard to guess as to what could be happening without getting a bit more detail from you. Do you think that your look is just as good, yet you're just not throwing the ball where/how you want? Are you losing the pocket? What is the ball doing that game compared to Games 1-2? Like others have asked, are you the only one seeing this big drop off, or is everyone struggling at the end? Answers to those questions will at least help us make some guesses as to what could be causing your struggles. Regardless, it's early in the season, so I wouldn't over-think it too much just yet. If you're still having this exact same problem 15 weeks from now, then we may have more to look at. For me, you're never in a slump until/unless you start telling yourself that you are.

Thanks for the answers guys. For the most part it is just me that has that big of a drop. Some are dropping a little but not that bad while others are able to keep it going. It's been a lot of flat 10's then will make an adjustment and wrap around the 10, another adjustment and may work for a frame or two. The first two weeks I was at 491 after 2 and did not shoot 700. I have tried different lines, different equipment, I have even tried different hand positions to see if that would help. I will try to pay better attention this week.

Lately I have been having mental issues for the 1st game as my family can not afford practice anymore

Life is full of things that need to be prioritized and kept in their proper perspective.  We love bowling, but it should never become "all consuming" to us. 

If you can't get to the center to practice, for whatever reason, you can still get a good practice session in mentally through visualization.  The best bowlers in the world visualize every shot "before they pull the trigger" and execute.  They anticipate (mentally) their ball reaction and so they are rarely surprised, unless they aren't fully engaged, as the pattern transitions.  I had to take several months off a couple years ago following a shoulder reconstruction.  I learned a lot about myself during the time when picking up a ball wasn't happening...

All too often we blame, or give credit, to Ball A or Ball B because we were great, or otherwise, during league.  In reality we were likely more attentive (or less) as the night went on.  Never underestimate what goes on between the ears.