I was thinking cal mag def tbh but have no idea how much to addHard to say. Could be but, that low on the plant say's natural leaf die off to me.
A pic of the whole plant would help.
Is this happening high up the plant?
Whats new growth look like?
It's in biobizz allmix (been in that about 3 week, started in lightmix, only been given 0.5ml grow and 1ml calmag (per litre) so far and it's just evaporated tap water, it seems to be throughout the plant and randomNope, I doubt it.
Whats the plant in as far as media?
What are you feeding?
Water source?
The whole plant pic says it's natural die off, as expected.....Good news for you!
The other answers will clear up any doubt...
It seems to be high up the plant for thatFirst call is 100% correct!
Normal leaf die off of early "starter" leaves.
Your golden!
It seems to be high up the plant for that
Even starting on some of the new ones
It's not just lower though as shown on the pics above.Perfectly normal healthy plants. Lower leaves don't stay looking perfect for long. They're usually a lot worse looking than that, if they haven't actually died and dropped off by that stage. Did you expect every leaf to stay perfect? Welcome to the real world. And to make sure there's no deficiencies all you need to do is use a hydro fertilizer, they contain everything in the right ratios.