My 1st Go Growing!

Had it all this week again - possible over watering signs I thought so dropped the amounts down and then some yellow tips on the Strawberry Banana so just plain pH downed 6.3 for her. But then at other points they have looked superb, all this on my 1st grow is a bit head frying to say the least and any advice, as always, is appreciated! Especialy as on day 21, when adjusting the LST on the Gorilla Cookies I snapped the main stem 2/3 of the way through above the 1st node.... I've wrapped her in duct tape and sealed with a cable tie and she looks to be ok but I'm worried she's still done for!? Was going to switch to 20/4 at flower but have done so the night of the incident to maximise her recovery as much as possible