Tomato Foliage/Cucumber Growth

Hi

Some of my tomato plants in the greenhouse,are showing discolouration on the lower leaves. They look like variegated leaves i.e. they have patches of pale green and white on them. I was wondering if I should feed  them with a general feed. As I read on here that the compost you buy does not contain much nutrients beyond the seed stage. They are about 18" tall and have a few sets of closed flowers on them. Also the cucumbers are not putting on much growth would they benefit from a feed. They are a long way off setting any fruit.

Thanks

Cucumbers like a decent feed... I give mine tomato fertiliser once a week and they are romping away with plenty of flowers and fruit coming along. I just water it in.