HELP/AYUDA!!! firts grow small yellow spot and leaves

If it doesn't spread, don't worry. Young plants often look young, even have some asymetry to them that they won't display later. They get prettier -- as long as you aren't overfeeding, keep doing what you are doing for now. Ca-Mg deficiences don't show up that fast -- impossible. they take weeks to display symptoms. So, it is definitely not a problem solved by cal-mag. get off that perspective as soon as yu can... the best thing to do when you see something is NOT try to be proactive and dump random shit into your coco. Always, ALWAYS know or be very certain before you add things... if you choose unwisely, it's always more difficult to deal with a toxicity or a problem that is now compounded with a new issue because of what you did to try to solve the first problem. Especially early on while you gain knowledge and experience. Be reactive... wait and see. if it gets worse, consider recent behaviours. If you are giving plent of Ca every week, it is not a Ca deficiency. Also, with a plant that young, you don't fertilize it -- in coco you may have it buffered with some nutes, but don't continue to fertilize the plant the first 2 weeks.. it has no roots... so, it's just dumping more grams of nutriens into the cooc that aren't being used and building up to unsafe levels. (just as it would in soil) So, if you have been feeding it since day one.. stop. Give water only irrigations for at least a week.