overwatering..... again???

Is this overwatering again???.... These plants are over a month old and are absolutely tiny... tallest one is 7” 5 sets of leaves including the first set they. completely lost.... they are all purple kush (short growing but didnt think this shirt so its definitely something im doing wrong) Im literally watering once a week because thats how long it takes for them to dry out to be nearly bone dry and I feel like watering once a week with nutes just isnt enough nutrients because they all are super light green in color? What do I do. My grow room is averaging 76 lights on and 65 lights offs and purple kush is a cold tolerante strain (so ive been told).... Shitty genetics? My first grow went 1000% times better in the exact same conditions and soil and maybe even colder. I must be an idiot or something as I have a meizhi 1200watt led for these guys (only using veg mode) which should be plenty!!! also I havent watered these guys in a week and they still not dry.... Ive been bringing them outside to dry quicker. This has been a brutal second grow for me. Im on time restaint and I have to put these guys in flower in 15 days. Can anyone put an estimate on how big/yeild they might turn out when finished based on current size?