Well where to begin man. Looks like you need quite a bit of help.
For starters lets get some lights in there that are actually used for growing. What kind of lights are those? Shop lights? I don't know about you but I don't think you are going to get much out of that other than maybe the fun of watching a plant reach for the stars because that is exactly what they are doing bro. See how tall and skinny those things are? Need to keep your lights close and surround the plant. She loves light. I would say get you some good lights and the ones that are over 4ft tall I would just pull those and start over. You should check out the cfl grow here it is really helpful and will grow some pretty decent plants. I am in no means knocking you and I understand you got left with some plants and have no idea what you are doing. It's ok man we have all been new to growing.
As far as watering you want to water only when pots are dry about 1" down in the pots. What I'm saying is that stick your finger into the soil and when its dry on the top 1" its usually time to water. MJ loves to be watered at the same time of day and the same days. Say like my watering schedule for instance I water every Sunday right at lights on and then again on Wednesday I water again right after lights on. Oh and for the lights 12/12 light cyle is used to induce flowering. Which I'm assuming that you are running 12/12 now which means they are trying to flower so when lights are off you don't want any light at all. Any light leaks will cause a hermie. A hermie is basically known as a lady gaga. aka it will have hairs and balls. You don't want that. Females will show 2 white hairs at the nodes of your plant while a male will show a cluster of little things that look like balls. Female=white hairs, Male=balls. You want only female unless of course you are trying to get seeds.
As far as how much to water them I like to water my plants until I see runoff at the bottom and then water on my regular schedule. The blue plant food is probably MG and that's not really some good stuff to be feeding your girls. Try to stay away from miracle grow. Try getting some better lights and nutrients and maybe give it a start over or continue on with this one and learn from your mistakes. We are all here to help and will help the best we can but you have to be willing to take forth the effort.
And also I'm sure it is just some bag seeds. Nothing wrong with that just need to have the right environment for your babies. Oh and don't feed them every 10 days. Feed them when they want fed. Watch your girl and see how she reacts. Start at low doses when feeding her so she doesn't get nute burn. Just watch the leaves and how she reacts. She likes temps between 70-80 and RH between 45-60 during veg and lower during flowering so you don't get mold. Keep your chin up man it will get easier as you go.
All in all I would say yank those tall ass ones and start over and get some better lights. Just start small and work your way up. If I missed anything sorry. I'm always here to help unless the missus gets mad at me for using the computer to much
Take care and smoke on bro