as long as the tip does not consume the entire leaf within two or three days and moves on to the next leaf, so forth and so on, then you should be fine, that is a pretty minor problem as it seems because your plants look like they are doing very healthy, remember as long you dont go over about 1.0 EC in veg you can feed your plant every other watering no problem, i use MYCO madness and MYCO maximum from Humboldt nutrients, these two products WILL DRAMATICALLY increase your plants vitality and YOUR YEILD WILL DRAMATICALLY INCREASE AS A RESULT ALSO, but as far as you go your plants actually look really good for NOT have using MYCO's and Enzyme's