Blackberries to small this year.?

Question:I have some 3rd year blackberries that are very small this year anyone know how I can improve size by next year? As a background I have 2nd year Raspberries growing in the same patch and they are normal size. It has been a dry year in zone 7 as well.

Answers:
Blackberries need lots or water to grow larger.
Do a little soil testing and see if you need some fertilizer.
I recommend worm casting as a fertilizer