1... Over Watering Young Plants
Young seedlings and cuttings don't need a lot of water after you have planted and watered them. Be sure to allow them to dry right out. This aids roots zone development as roots go in search of water. A good way to remember is if the soil looks damp it doesn't need watering, after all, if your flowerbed outside was wet after it had rained you wouldn't go out with the watering can!
George says "Over watering equals slow growth."
2... Your Extraction Needs To Be Above Your Lights
This mistake is a common one as people are often worried that the weight of the filter will snap the tent or they are worried about hanging it from the ceiling. This mistake can affect your plants in a big way as the heat from the lights are pulled up and away from your plants.
Gareth says "Excessive heat effects your yields."
3... Overfeeding Your Plants
This mistake is often made as people assume if they feed double the nutrient they get double yield... WRONG... when you overfeed a plant it seriously damages the plant. A much safer option is to feed the plant less than you think it needs and give it more when it becomes clear it needs more.
Ben says "Overfeeding plants will effect your yield."
4... Forgetting To Watch It Doesn't Get Too Cold
With winter approaching it's very easy to forget that the temperatures when your lights go off are also important. Plants that get below 16 degrees risk going into shock and will stop growing so be sure to have heaters come on when your lights go off.
Jack says "Shock from cold temperature will stop your plants growing."
5... Not Making A Checklist
More often than not grow room issues can be avoided by having a simple checklist that you check once a week, e.g. temperatures min/max, is there any bugs? By checking regularly you can avoid problems - prevention is a lot cheaper and easier than trying to fix an issue once you have one.
George says "Grow smart, try to avoid avoid problems"