Lower leaves wilting turning yellow/brown

Strain is AK-47 and plants are about 3 weeks old. Using 130W CFL's and growing in perlite/coco (25/75) with a layer of perlite on top of the pot. I'm using cyco nutes feeding at 0.6 EC in 10 gallon smartpots.

The plants started to have a bit of an issue before I up-potted them, the first set of 3 pronged leaves started to go a bit pale yellow and had a brown spot or two appear near the leaf margins. At this stage the plants looked a lil root bound but I have since up-potted and they haven't come good and have not grown at all.

I flushed my medium last night with plain water at 6.0PH and tested the run off which was at about 6.1-6.2ph so I think my root ph is good. I reckon this may be a root issue but really don't know how to proceed from here. I watered them with a EWC tea and some nutrients at 0.9EC last night after the flush and the yellowing and browning has still continued to progress with the 3 pronged leaves now folding over on themselves and looking about to drop off.

nute lockout possibly?

To help anyone else having dramas, I have seen a bit of a recovery after flushing the shit outta the plants in the shower and then giving a light feed. The yellowing and spotting of the leaves seems to have basically ceased and new growth looks good and vigor is starting to return.

My guess was nutrient lockout by one or more nutrients because I wasn't feeding with enough run off I reckon. I'm going to flush them all again tomorrow as that will be 6 days since the last flush/feeding and see how they continue to go. If there is no more sign of problems in the next week or so and they continue to progress along nicely I will call this problem solved and chalk it up as a another plant issue fixed with proper flushing