Just as i wanted to flip to 12-12, need some help identifying issues.

[shpongler]

So, i've been working my ass of lately and finaly came around to feeding the plants. I noticed one of the my two plants was in bad shape...
They are both the same strain but only 1 is showing these signs (hopefully the other wont follow)
Same soil and everything

I kow they are kinda thirsty and look hungry for N - i just gave them water and nutes, as mentioned before, i have been on the road more than i've been at home last weeks so it's been difficult to keep up with the care for them.

Anyone has an idea what i have to look for ? Going to test soil ph later today when i have the time. Last time i checked soil ph it was around 6.1

 

[Opie1971]

Looks underfed and overwatered at some point

 

[shpongler]

Looks underfed and overwatered at some point

I'm pretty sure i'm underfeeding them, and also was overwatering at some point.
I didn't know overwatering could cause these symptons after a while.

So basicaly now i just give nutes with every watering and try not to overwater and hope for a good recovery? maybe wait another 1-2 weeks with flipping to 12-12?