All this advice is good.
I use a mixture of diaries, wall planner, notes on my phone, and dry wipe boards in the grow room.
Definitely tag each and every plant from birth. If you're working from scratch and chasing phenos from multiple seeds then make sure you can tell lineage on these tags. I use a codify my tags: starting with two initials for the strain (ie. LY for Larry OG), seed number from the original set (i.e. LY3), then a letter for whatever run cycle we are at (ie. LY3D tells me its the fourth cycle), and finally number identifies the plant number in that run (ie. LY3D6).
I use different color pen for each strain, both on the tag and on my paperwork so I know at a glance what i'm dealing with. Sounds complicated but it doesn't take long for this to sink in and become second nature. This is the only way I can keep lots of plants in a multi-strain garden properly organized, and I only have a 3kw flower room.
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I built my own spreadsheet diary to make records for each strain table. I print it, put on a clipboard and keep with every strain table for the life of those plants.
Every row in the sheet is a day, and every day in dedicated columns I note min/max temps & humidity, pH and EC of reservoir, of runoff and of any new feed, including foliars and teas etc. I make brief notes on growth / leaf and plant health and anything else noteworthy.
At a glance I can see veg has been XX days, flower sites set in XX days, etc. At the end of the run I use a different sheet to summarize the outcomes: plant size & health, yield, quality etc.
I don't know where I would be without good quality notes like this. Happy to share the sheet if you feel like it would be useful in your case.