Lettuce issues

I had a go at growing lettuce last year, I grew them in containers but they didn't do very well and never got very big or beyond a few leaves, they we're cos lettuce and never got any heart to them.

I'm trying again this year but worried they won't come to much again. I have seeded cos lettuce seeds into a tray of seed compost. I have had them in the greenhouse and after 2 weeks they got about an inch high so I pricked them out into cells (tray of 24 cells)

This was last weekend, they look fine but do not seem to of gwown much at all in the last week. They are still in the greenhouse.

I know not much is growing fast at the moment due to the weather but should I be feeding them or doing anything differently?

My greenhouse got very warm today. It just touched 90deg with the auto window fully open. Do you think it is to warm for the lettuce?  Should I stick the tray of cells out in the garden during the day.

Going to order some greenhouse shading tomorrow as its a 6x6 greenhouse and gets hot pretty quickly in the sun (when it comes out of course)

They would be better off planted some where, especially if you can plant them somewhere sheltered from the worst of the weather.

Mine are protected from the worst of the rain by a fence and are growing, not quickly, but steadily.