First lets start with the basics- lighting, food, air and water. What kind of lighting are you using? How far are your plants from the light? In my opinion I would keep them under flo's (3-4 inches from light) until they are about at least 6-8 inches tall, then move them to your hps lighting if your using that type of lighting (p.s. don't fall into the hype of new LED's, they suck and don't produce the lumens this type of plant desires). Second lets talk about the medium that you have them in? Are you using a store bought brand like miracle grow or something to that effect from say like walmart or homedepot or are you using professional grade mix? Store bought brands like the ones I mentioned aren't very good because they use cheap ingredients and most of the food in them are time released which you don't want, you want to know exactly how much your feeding your ladies and exactly when your feeding them. Let the pots dry out completely betweed waterings, just lift your plant and you can pretty much tell by the weight when they need watering, over watering will fuck up your ladies, the roots don't like to stay wet all the time. I've been gardening for about 9 years and have tried all different types of food from the cheapest to the most expensive and found that you get exactly what you pay for, go with a good line like fox farm, AN, botanicare ex..... Do a little research on different foods, the net is a great place to find lots of info on this subject. If your plants are yellowing it depends on where the yellowing in starting, if it is starting from the bottom and moving up that usually means that you have a nitrogen def which means you need to get those ladies more nitrogen, if the yellowing is consuming your whole plant then you might have a nute lockup from feeding them too much, when they are babies they don't need full strength feedings, start with about half the recommended dosage and go on from there. If this is the case then you shoud flush you pots with plain water and feed with half strength, and let the soil dry completely before next watering. Next what is your air quality? Do you have them in a closet, open room, window or what. Plants need fresh air and co2(which is in fresh air) to grow, which in mother nature is naturally available but inside you have to mimic mother nature. Make sure you have a fresh air supply either from outside or supp co2. Last things we will talk about now is heat? What is the temp in you area, should be between 72-80 degrees f, high and low if possible? Venting your room is very important to remove heat, fans work great but you need somewhere for the hot air to escape to. One last thing you might wanna test your water for ph and other things that could be causing problems like hard water, chlorine content and so on because if your water quality is shitty then your plants won't be able absorb the food from the water, the plant will just lock it out. The best advise I can give you is to grow every day of your life, read every bit of info you can and the most important thing is that you will learn from trial and error, you will learn to be able to see what your ladies need just by looking at them. And make sure your using good genitics and work with the same strain til you know that strain in and out and then you will be successful. Hope this helps.....