HELP WISPY AND STRETCHY

I need help what is going on with these 4 week old sour diesel's & purps in hydro? Looked very squat and bushy in the first weeks then started the strech. Temp is 60-72. Fresh air in & out . 5 plants in 4inch cubes on top of 12inch slabs. Were in veg under 400mh for 2 wks then hps for around 10 days. Got 3 & a quarter oz of same sour stock 2mo ago?? purps seam to be a hit & miss thing as they like to do the wispey thing sometimes....have got 4oz per plant in 5gal soil pots with this same stock Purps plant as well. Please help ??