Help please

[growgreen755]

Trying to figure out what deficiency or problem this is Ph is 5.8 and im using fox farm nutrients at 1/4 strength. yet it looks like im about to lose the smaller one. I water drip four times a day for 15 minutes, before that i was going it on for an hour off for 2-3 but i thought that was too much. Can anyone diagnose this for me?

 

[growgreen755]

just super cropped one of my plants and i did it to the main stem. It is healing but you can see right through the stem... is that a problem? I had it taped for around 4 days.