Extremely slow growth. Im near week 2. Water is P...

Coco should be phed from 5.5-6.0. Ive gone up to 6.1 without issues but once i hot 6.2 for multiple feedings i had slower growth and unhappy plants. You should also be feeding more than 180ppm at this point. I usually feed 250ppm at the start and week 2 i bump up to about 350-400ppm. Seeing as they are about the size of a 1 week old i would bump up to 300ppm. Also if you arent already you should be keeping the coco wet and not letting it dry out too much or your ph will go all crazy and other issues will occur. I water every 1-3 days depending on plant stage and how big its root system is. Your temps are also a bit low. You wanna be around 24C for optimal growth. Another thing that heavily affects growth is lighting. You dont say what kind of lighting you have but it looks like a blue/red led light. Those are very notorious for lying about their output. You could buy one that says its equivalent to 1000w hos when in reality it only draws 150w and is thus equivalent to a 150w hps. Always go by wattage draw for "cheap" leds. You want 50w/sqft for "cheap" leds and of you go with high-end leds you only need 30w/sqft.