Last balls drilled were 15 lb 5 oz before that they were 15 lb 3 oz balls feels alot heavier now or is it just my imagantion.

I've never been able to tell the difference in a few ounces, you talking about less than 1% of a difference in weight.

Usually it's something being slightly different in fitment that causes a ball to feel heavier from my experiences.

I would agree. Probably a slightly different fit would be my first hunch. 

Did you double check the weight vs what it said on the box?  I have seen variations there due to the wrong ball being put in the wrong box or other human error.

 Last balls drilled were 15 lb 5 oz before that they were 15 lb 3 oz balls feels alot heavier now or is it just my imagination.

One minor aspect is unlikely but possible: if the drilling for your hand is shorter or the holes a little too larger, the ball will feel heavier.
That's like when a new bowler uses and alley ball not drilled with a food fit. If they get a new ball drilled for their hand, they will usually be able to handle a ball 1 - 2 pounds heavier than the weight they use when they pick up a ball ff the racks.

If the ball is drilled to fit you properly, you should hardly be able to feel a 2 oz. difference.

I will check out all above i was also considering that the box maybe wrong and also the span being shorter but forgot to mention i am 70 years old.