If you do decide to mess with pH or EC, I'd recommend going for pH first. Burn is quite easy to avoid with a measuring jug. As soon as the jagged tips of the leaves show that yellowing / fading, dilute the solution 10% or 20%. Never push it with the concentrate and measuring it out, what it says on the pack is the max you should go for. If anything, use a few % or so less. Burn shouldn't be a problem if you're conservative with the nutrient, and being a few percent below the max it says on the pack is unlikely to do anything you can even see to the yield / growth rate. pH is harder to do by eye but plays a big role in nutrient availability.