stunted growth / burning older leaves first

You are doing too much and feeding too much of too many things. Baby plants need baby feeding, what you are giving them is akin to a 10 course banquet, it won't make them grow faster, just burn them. They only need quarter to half strength nutrients at this stage and not until they have 4-6 nodes. The soil you are using should have enough goodness for the first 3-4 weeks of growth without the need for any extra feeding. Try just giving them plain water until normal growth resumes, then choose one or two nutrients only and at quarter strength for a week or three before upping the feeding slightly. Force feeding your plants and feeding them a whole factory of nutrients will not make them grow faster. Patience my friend! Hope this helps, Organoman.