PH /Lockout advice needed

I am in Veg 44 day from seed , being a newbie I need adive , Im in hydro about a week ago I did a res change and brang my ppm up . Then 24 hrs later I noticed a problem. UP untill then the plants looked very healthy with no ill signs (nice and green ) but stunted growth, I did some research on my plants condition , and I felt it was a Iron def, after a little more research I found my PH pen to be defective and all along I was running a ph of 6.3 and summed my problem up to microbs being locked out, from PH being to high for hydro, In the last week Ive have seen really good foliage groth and some stretch but not much,I was wondering if I should intervene with rasing my MH light and or go to HPS to promote some strech,or wait it out and leave well enough alone . the first picture is 1 week ago before rectifying the lockout and the other 2 were taken today. Thanks

I know this is an old post but, she looks beautiful. I stay under mh until 3rd week of flower. It keeps my height down. By this time they are pretty much done stretching and start putting on mass.