Most problems arise because watering is not being done correctly.
When I water, I wait for the pot to become light, and I also feel the cellular strength of the plant, I feel if the leaves are "soft" or "hard". I also examine their fatigue and posture, when they are slightly drooped and the pot is light, I know it's time to water. For my 5-7 gallon pots I normally water with about 1.5 gallons to the point of run off, I let it soak so the roots are saturated completely, I then feed with the nutrient solution, but much more slowly on the feeder roots, allowing uptake easier. You shouldn't really need to be watering everyday in a large volume of soil, it should be able to last days, or even up to a week depending on the conditions , or weather (outside).
The roots in the first few inches of soil are not the same as the roots at the bottom.
The roots at the top have fine hairs that uptake water and minerals better, known as the feeder roots.
The roots below are the structural roots which are more responsible for anchoring the plant into the medium, they will have less fine hairs.
I would say to start watering more diligently, don't use cups, use a watering can and get something to collect the drain off. I would say to order some concentrated sea-weed for gardens, it really is an amazing foliar spray, especially helps "tingle the root zone" and promotes bacterial activity around those fine hairs...
Just my two cents though
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