No way those leaves are underlit, 250enviro and t5's, i use all these and that is enough light believe me. With 5 more weeks veg this is gona be tall and give lots of lower crappy bud, id consider pruning and topping so always an option to control the height.
Did the flush make things worse? this might indicate underfeeding.
There are always a lot of conflicting points, i may be wrong but as always you need to address one thing at a time, if increased ferts dont work with the bioessentials then.
Problem solving plants is a skill in itself, you may not get it right first time and the plant will suffer maybe even die but what your aiming to do is eliminate the possibilities.
I use that westlands sh!te soil and get some pH problems after a while, i add lime to mine but i use the standard westlands seedling and flowering soils. Too much peat for my liking, i have to add 25 to 30 percent perlite and vermiculite to get good drainage. I would say these soils need a little liming before use but they generally are ok, i find most westlands soil is pH6.3 straight out of the bag so not great to start with either. You dont need a hps to flower with straight away, the enviro will start you off fine. If you can control the heat use the enviro, hps and t5's to flower with, should increase yeild s bit over just the hps, make sure it is all wired safe with contractors if you do as it is a lot of ampage.
Height is gona be an issue soon i think, 5 more weeks of veg is a monster plant! Peace