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I am having some problems with my mini tomato (cherry tomato) plants. The leaves develop purple spots and purple leaf edges and some are now turning brown on the tips of leaves. They are grown in an greenhouse with day temperatures between 25-32 Celsius and night tempuratures of 12-18 Celsius. The problem started on lower (oldest) leaves but is now present throughout the plant to varying degrees. The upper leaves and stems have also taken on a slight purplish hue especially on the undersides of leaves. The initial soil test taken before planting did not show any real signs of deficiency and a standard amount of organic fertilizer was applied. Also, the plants have what seems to be a very large amount of fruit branches and flowers on the upper half of the plants. The tops (flower leaves?) on some fruit appear dark. Most leaf discoloration appears on the sun exposed surfaces.
I am hoping this is not a disease bur rather a deficiency that can be corrected. Any ideas what it could be? Thanks!

Some more...

It’s a good idea to fertilize again when they start blooming. What were the NPK values of the organic fertilizer you used at planting? After blooming so much, I think they might have depleted what was there. Are they planted in the ground inside the greenhouse or in containers?

Thanks for the reply.
Initial fertilization consisted of a mix of organic amendments. Fermented chicken manure of 3-4-2, fermented rapeseed oil cake of 5-2-1, bokashi, and agricultural lime. Ten days after the second set of flowers began to bloom a foliar application of 6-8-4 was used. Copper fungicide has been applied on 10 day intervals since the first flowers appeared.
The plants are growing in the soil, deep-planted, under silver plastic mulch. I water with low-pressure (though faster than drip) irrigation system that is under the mulch. These particular tomatoes receive what would be around 4.5 liters of water each, per week.