Since this involves to phones I did not want to duplicate it and put it under 2 different phones but have you tried these suggestions and have they worked for you. This is for the iPhone 4 & 4S.
There is an article on the Blog about this as well.
Top 5 tips to speed up an iPhone 4 or iPhone 4s running iOS 7 | iMore
There is an article on the Blog about this as well.
Top 5 tips to speed up an iPhone 4 or iPhone 4s running iOS 7 | iMore