Should I have waited longer to add a diluted nutri...

It seems like you are growing in coco or another soilless medium correct? If so then you are fine. If it is soil then you could have waited another week or 2 maybe, but I doubt it will hurt them much the way you did it. Also If you are in a soilless medium you can feed sooner. In coco, I feed as soon as day 3 depending on the stain and how quickly they develop their first true leaves. In soilless medium, you also want to make sure it doesn't dry out as you would want with soil. Too dry of soilless medium can cause the build-up of nutrient salts and mess with the ph of the medium leading to nutrient lockout. It can also sometimes cause dry pockets/channels of the medium that won't get wet when you water, killing roots and overall causing issues. Growing in coco I water every 1-3 days(feeding nutes every watering) depending on pot size and stage of growth. I also always water until 20% runoff to make sure I am leaching out all the old nutes and replacing them with fresh nutes. It also allows me to check my runoff ph and ppm to make sure I am feeding properly. Runoff ppm that is higher than what is going in means that you are feeding too much as well as not getting enough runoff to flush old nutes. Overall your plants look like they are doing okay, just small for their age. Check out my diaries to see what my plants looked like week 3. I would guess that your light is either too far away or not strong enough for them. They are looking pretty stretched which is a big indicator of not enough light. It could also be the fact that you waited 2 weeks to feed nutes if you are in soilless as soilless generally has no initial nutrition for the plants. I hope this information helps a lot and good luck with the grow!