Heres what i do bro:
Phone
1. I have a widget on my phone that counts days "day counter", i put 4 counters up on my last screen and i always know what day they are on.
2.I also have a app called "note everything" that i record all my feedings and measurements.so at the end of my grow i can look and tell you every thing that went into my girls and when.
Dry Erase Board:
I have regular one and one that is a calender
the regular one i keep every plants last feed on, so when im mixing up nutes i have a quick referance, i just look up on the wall to what i gave them last time and what i should be giving them next time. then i erase the last feed and put up the new feed and start all over again, i feel if i have time to mix nute i have time to record on the board what i put in the mix, also this helps with my note everything app because some times ill forget to record in my phone the day i fed them so i can always go back and check this to make sure i have my feeding log up to date.
The calender i used to keep track of the days between feeds so i can clearly see how long they are going between feeds.
( i got both for about 5 bucks at walgreens)
Notebook: this is where i keep track of all the extra details about strains, like smells, growth and how long it took to sex/flower,how well they feed,height,final yeild. each strain gets their own page and i make sure to jot down everything i can about them.
Thats how i keep track of my girls.:Sharing One: