first time grower - lemon kush

first off i'd like to thank everyone at this site, this is my first time posting but i've read the site for a lot of months trying to absorb all the knowledge everyone has shared, it has been extremely helpful. so unto my grow...

i got some lemon kush seed earlier last month from a good seed bank i read off GC, i gathered up all the materials i needed over the course of the month and got them germinated and planted 4 of them on November 30th. i used fox farm potting soil and haven't given them anything else except water, right now it seems to be like every 3 days they're thirsty again and i usually split a 24oz bottle of purified water between the 4 of them, i'm not sure if that is enough but anymore and it seems like it would drown them. the room seems to stay nicely at around 80 degrees, but i put in a fan because i added a couple more CFLs, all my CFLs over my plants right now are daylights which i read are good for vegging and then i read i should switch to the cools when flowering? i know CFLs aren't the greatest for growing. i have about 200 watts over them right now but have more to give them once i transplant them into a larger home. so hopefully i've given you guys enough info before my questions. i'm wondering how much longer i have to go before i should put these guys in a larger pot. another question is the one has some yellowing on it's tips but other then that the plant looks healthy, i can't tell if i should be worried or not. also i read different things about ferts and nutes, do you give them both to your plant or one or the other? i bought a PH tester called bluelab PH pen and it was pretty pricey but i'm wondering when i should start testing them. sorry for the long read if it was too much