Six 600-watt hps bulbs in use? If that is the case, it could be way too much light. only need about 50w / sq ft for HPS, i believe... google to verify. efficacy of bulbs may vary and that guesstimate will vary along with it. More efficient Led are 30-35w/sqft to show this watts/sqft has severe limitations and is not an apples to apples comparison.
first, make sure temp or rh is not out of whack... pH test slurry of soil or some runoff to get a hint of medium's pH. If you haven't pH after you mix fertilizer. Soil can correct these things, but if it is WAY off, it's not going to fix that. every 1 whole integer is 10x strength of previous (acid or base, depending on direction, and if straddling 7, does that hold? bwahaha, no matter "7" is safe for soil). if it's "4" or "10", you may not want to rely on the soil correcting ph, for example. i could be wrong.. this is a number pulled out of a hat and may vary quite a bit relative to soil in use.
soil -- it's a balancing act. it varies greatly as far as how much nutrients are present from the get-go. as those diminish, you slowly raise feeding -- either frequency or concentration, you can accomplish same thing both ways or in combination. if your soil is lacking something, you may need to boost that 1 component a bit. this takes trial and error and familiarity with the products you are using.
every other day could be fine... it is easier to add than it is to take away, so i'd try backing off, first... see what happens. there is more than one thing visible, so i'd bet on pH or lockout, if there isn't a massive amount of light from 6 600w hps bulbs in small area. Something that causes multiple symptoms tpyically associated with 1 molecule, but in this case you probably have plenty of it. ... ph or a nute locking out others.