Soy consciente que a las plantas les faltan horas ...

A little small perhaps but the correct amount of leaves. It also looks a bit pale indicating more light could be used. But are you outside already with these? You are right nobody who grows outside is going to get the 18 hours they talk about using inside. Starting this late I'm also assuming this to be an auto plant as unless you're on the other side of the planet, you have the season backward. I start the first day of spring (3/21) for sprouting, use artificial light in my Mondi greenhouse only till plants throw true leaves. Then they go outside using sunshades to control how much light they get. (this must be watched diligently as to not burn them) I vary the layers of sunscreen plastic (auto window tint stuff) to match the lumen output I want to reach the plants using a light meter. More work but the sun is the king source of full-spectrum light and worth the extra time. In the time you mention my seedlings have reached the lid of the greenhouse and are "set free" from there on out, while still monitoring the amount of light they get until the third true leaf set is thrown. Then it's full power until it reaches over 90'F outside when sun shade becomes important to cool the plants. I move mine inside when temps get over 90F. Good Luck and Stay Safe!