With lettuce I'm not sure if you might have lettuce that can grow in the type of heat you get down in your area. With lettuce I have grown (green leaf and red leaf)as long as high temperature during the day is around 80 degrees they will thrive in full day sun. In temps 85+ degrees they grow slowly until they start flowering even in the shade. They need cooler temps to grow so you might want to get prepared down the line to move them into the house. They will do just fine either by a window or by using florescent
grow lights. If you are going to keep them outdoors in a shaded area during the summer try to get as many seedlings started now so they are at least 2-4 inches tall when the heat arrives. You should have lettuce all summer.
Your plants are looking really good! The lettuce will be shooting up and spreading out pretty fast. The tomatoes are looking great!
With your clones if you want to slow down the growth process cutting the roots down short will do the trick. If you want to slow them down for a month cut the roots almost up to net pots. If you want to slow them down about 2 weeks cut 1/2 the full length. You should only test this on 1 plant as your tomato plants and climate is different than mine so you might end up with different results.