By Balcony
Cambs,
United Kingdom 
My son came to see us today & he brought a leaf from one of his tomato plants that has purplish blotches all over it & some of them have perforated the leaf. He told me the plants get watered everyday & he gives them tomato fertilizer once a week. At least half the day they are in full sunshine though there is no sign of sun scold on the leaf he gave me. He also said most of the plant had leaves like this one but seems to be growing strongly & has already reached over 1.5m (5ft) tall. It is bearing ripening tomatoes.
Can anyone identify the problem & suggest a possible solution?
23 Jul, 2016
Answers
Have a go at Googling septoria leaf spot.
24 Jul, 2016
Thank you for your replies but I don't believe the problem is Septoria leaf - the photos I've seen & the descriptions look nothing like the problem with my son's tomato plants.
I'm beginning to think it may be temperature related due to the cold start we had to July this year.
The plants were bought by my daughter-in-law & have always shown very strong growth. They have looked very healthy up until now. I haven't seen them for myself for nearly a month but my son sent me several photos of them while we were in Spain & they looked very healthy. If this problem had occurred earlier he would have asked me for advice just like he did on Saturday.
It's a problem I've never seen before on tomatoes & I've been growing a few plants on our balconies, in Spain as well as here in the UK, for the better part of the last 40 years! I was used to seeing early & late blight on tomatoes on the allotment & perhaps other leaf spots on my tomatoes but I've never come across this particular problem before.
24 Jul, 2016
This looks like bacterial spot which comes from bad seed. The spores lay dormant in the seed until it germinates. I'm not aware of any remedy, Very sorry.
24 Jul, 2016