As edjones indicates,you must prune out the canes that have fruited,bur DO NOT prune out the new canes that have not fruited,these are the fruit bearing canes for next year.
IF you appear to have NO new canes,as may be possible if your raspberry bed is now congested,then you can cut ALL the canes down the ground,but you probably won't have any fruit next year;and will have to wait till the following year for the canes to recover.
We NEVER feed our raspberries,as we would probably get lush growth and little fruit.
Temperatures can affect fruit growth,but not to the extent of few berries(again that sounds like overfeeding).This year just as the raspberries wer setting we had a really hot spell,this was followed by one short,intense fruiting.After approx 6 weeks the fruits were over.This was at the end of June.
Usually our raspberries are late fruiting (August/Sept) and on till the first frosts,So you can see temperatur conditions can affect the fruit.
I wouldn't rip out the bed,just cut back the canes as suggested,and see what happens next year.
However,do stop feeding them.They will only put on too much leaf and little fruit.
ON the whole raspberries are great fruit,needing very little attention,except as stated above.
Good Luck.