I didn't realise lettuce can grow like this if not harvested. I've grown a patch this year, but they're not the most economical plant to grow because lettuce is very cheap in the shops. However the freshly cut lettuce smells so nice.
It's a pity about your tomatoes and the lack of rain. Have you considered mulching them to retain moisture?
I always let my lettuce go to seed .. the flowers are great for insects and then I harvest the seed. I need to do it again this season to collect for the new garden as I usually rely on self seeding.
I left some lettuce plants, and I harvested only the bottom leaves daily. This was also the first time I'd seen lettuce plants mature and start flowering. The leaves were becoming similar to kale, hehe.
I'm considering adding a shade netting of around 50-65 percent on top. As for mulch, I don't think it's suitable in my area because it could become a nest for ants and other insects that could harm the plant's roots.