Ive got a few from my current grow (first in 10 years)
Started with an Aerogarden. Added Aerogarden nutes right away, burned the little bastards, they recovered barely.
Got Fax Farm nutes and ignored all that said use 1/2 strength, went full strength and burned em again.
Didnt realize Fox Farm nutes have no calcium and I use RO water (no calcium) and got a calcium deficiency, had to add Cal Mag.
Then stayed in denial about a thrips problem too long and they took over, eating entire fan leaves. Then I transfered to 5 gallon DWC buckets and put mosquito dunks in the tank ( I heard to water with dunks for thrips) The grainy shit got all tangled up in the roots, made them stick togethor and then turned in to root rot on 2 of 3 plants. The roots completely fell off one one 4 weeks in to flower. It was my biggest at the time but stopped growing to regrow roots, and clearly stunted severely. Curently 7 weeks in to flowering, the one that the roots didnt fall off, recently yellowed and dropped 95% of the fan leaves, and it looks like a fluffy dog that got wet, and is half the size it once was, and its depressing. Since it has no more fan leaves and doesnt look like it will recover, I chopped half of it today, and started a water cure cause I didnt have time to flush, and at least I salvaged a small harvest.
Made a DIY bubble cloner and didnt block out all the light a they all got "clone snot" and died.
Tried to germ some Aurora Indica and Papaya seeds in a room that got in to the 60's and neither would germ.
I think thats about it but Im sure I have more I forgot.
FYI thanks for posting this it did make me feel better, I thought I was a total fuckup.