What’s wrong with my plants?

Hello, as you can see my plants (Jamaican bell, lemon drop, wiri wiri) are in a grow box, approx 20°c, slightly wet ground. The light is a 100w plant led panel. I think something's missing, because they grow slow (they are around 40 days old). The Veins of the leafs looking bold and the lower leafs are falling off.
What do you think?