Browning of stem and mould on dead leaves

What do you think is the main fault here?
It's in a greenhouse – current temps at 14-25. First month everything grew well.

Wondering if i should rip it out and start again. My wombok have decent new leaves but tend to grow brown and get mould on tips.

The pakchoy at the start has really dark leaves that are quite firm with slight browning lines on the stems.

The brocolini seems really happy though..