PH in the 5's is not cool with soil, yea they do make soil PH meters, they have long metal stakes usually measures PH lumens and moisture, really only good for checking for watering, my suggestion is the basic one, especially when we have trouble identifying what the issue is, flush it, 1 gallon pots need 3 gallons of water, but make sure you PH the water up to the 6's, if you use drops to test get it in the gold area, during the flush check the drainage runoff PH , this will let you know exactly what the soil PH is, aside from the original water PH, you may have a salt build up if you havent flushed from all the feedings from day one, this can cause your PH to get outa whack and locking out nutrients, from looking at your pixs your atleast halfway thru flowering right? when dealing with soil i get great results flushing for maintenance monthly, would be shocked how much salt builds up, also PH in the 5's will lockout nutrients, for hydro mid 5's are ok not for soil, i am certain this is the issue, as for your light, get as close as you can without burning your hand, i use air cooled hoods too and i can get atleast 6-8inch , also how far along are you into flower? also im just babbling cut back on the nutrients next feed just a bit, good luck you should be good to go after the flush
