Raw detection just based on the pictures is not reliable and most of the time the answers are wrong, a full lab experiments plus  pathogenecity tests in glasshouse are required.

But as I teach vegetable diseases in here, i guess, this is very similar to "Buckeye rot of tomato". the causal agent for that disease is phytophthora.  If you search in the google for this disease you can see very similar symptom to yours, Also in the second picture, on red color tomato the sun-scald disorder can be seen.

hi

the pictures are not very clear as you have focused on whole plant..the leaves looks fine..and the purpling of fruits is related to genotype and temperature. 

I agree with Sharma. This is a natural color change related to the genotype. It occurs  before ripening. 

In the picture, the symptoms are no clear The rot by Phytophthora has brown color similiar to yours, but  besides shows characteristic rings or zones of growth and different line or border of rot. It is very important the work in the laboratory and the record of information about the genotype and the conditions of orchard.