Hey Kmoo, ur plants are definitely suffering the symptoms of an over-watered plant.. Though u may have cut back on their actual amount of water, the problem is still there, so we must look @ other causes..
Look @ it this way - an overwatered plant looks the way it does not because of the amount of water, but because of the oxygen content of the solution or the amount of oxygen the roots can utilise (this is why DWC growers don't usually suffer overwatering).
My educated guess is that u mix ur feed in a 20L bucket and use it up slowly over the week??
If so then u are depleting ur water of oxygen as it sits there waiting 2b used.
How do we fix it now?
Add some Hydrogen Peroxide. The H2O2 mixture will ensure rapid root recovery.
Some people say not to add it to soil as it degrades beneficial bacteria, but @ this point ur plants aren't benefitting from that bacteria anyway, so we'll fix this problem & worry about that if it occurs..
How do we stop it happening in the future?
Add an airstone 2 ur Bucket mix in order to increase the 'O2' levels.
..Or make a smaller mix that will be used within a day or 2.
Hope this helps