those marks are more than likely from watering too frequently.I think that the plant is going well.However what kind of problem is this burn on the leaves. Also i think that i found why there are yellow leaves on the bottom of some plants.
I noticed that some plants are drinking they nutrient solution faster than others and then they start drawing nutrients from the leaves.So the yellowing of the leaves is connected with drier soil. Now i water all of then more often.
yellowing at the bottom could be related or she needs a bit more nutrients..
as you increased your watering did those marks show up 4/5 days later?
what is your feeding nutrients and how much?