Dont change ball weights.
The problem is you are coming up to the pocket too light, basically the ball doesnt get the desired entry angle into the pins or retain enough energy to carry the 5. Generally it happens because your ball isnt finishing strongly.
Its difficult to say without seeing the reaciton in person, but if it is continually happening (ie you keep leaving the 5 pin) it will usually come from 1 of 2 areas.
1) Ball is moving out into the dry, hooks, then releases all its energy too early and doesnt finish strongly in the backend leaving a weak hit on the pocket.
2) Ball is skidding through, doesnt have a chance to make the turn and ends up coming up light and leaving the 5 pin.
There is a number 3 to the above too (so i guess it is 3 areas), and that is your targeting is off and the ball simply doesnt hook back far enough towards the pocket.
It would be an idea to get someone with a little experience to have a look at your ball as it travels down the lane, see what sort of reaction you get and what the pin carry is like. But for the above you can try a couple of things.
If its hitting the dry and dying, move yourself and your target left a few boards. This should help you get into more oil on the lanes and help the ball retain energy to finish strongly when it reaches the pocket. Keep in mind you may find your ball doesnt seem to hook as strongly as before, but that is the intended reaction.
If its skidding through it can be for a number of reasons;
The lanes have a lot of oil on them in the part you are playing on so your ball just doesnt have enough chance to hit the dry part of the lane and start working. You can experiment by moving both yourself and your target right a few boards to help get you out into the drier part of the lane. You may wish to look at your ball, perhaps the ball simply isnt strong enough for wetter lanes and you could do with something more aggressive that is going to hook more, or you could alter the coverstock of the ball by sanding it to produce a rougher surface.
The others are really personal things (and they tie in with the above), your ball speed might be too high and you simply dont give your ball enough time to work before reaching the backend. What happens is the speed of the ball actually overpowers the revs you generate, forcing the ball to go longer down the lane before trying to hook back towards the pocket.
If you have a high ball speed, you can try adjusting your speed a little by lowering the position of the ball during your stance on the approach (instead of chest high, drop it down a couple of inches towards your waist) or by slowing your foot speed on the approach. However if you are still fairly new to bowling or (i dont know how else to say this) your skill levels are at an intermediate level, it really isnt a good idea to mess with your timing as it can cause more problems than it fixes.
Start by trying the movements i suggested anyway, it might be enough to sort out your problem. However if you are looking for a long term solution i suggest you invest in a coach (your local centre should be able to suggest someone, or perhaps try the people you bowl with). Things like this really need someone there in person to examine what is happening and a coach is the perfect solution
