Is this a problem?

Looks pretty normal. I'd give it some time and see where it goes. Is it localized to one leaf? Sometimes I cut off leaves that look funny or have spots.

 

You shouldn't be transplanting a 2 week old plant or giving it nutes. It's not even had time to develop a solid root system and become stabilized in that length of time much less need repotting. It's always best to leave them in the container they are in until they become slightly root bound. This is usually when the plant itself becomes larger than the container it's in (wider and taller). You've stressed the plant pretty good and these leaves where you are seeing discoloration are going to die off....most likely from nute burn. Fresh soil...I'm assuming Coco too although I've never used it personally, is going to have some nutes in it fresh out of the bag so there is absolutely no need to give a new plant anything other than properly pH'd water until it has had the opportunity to use up what is naturally in the soil. Nutes are plant food. If the soil has food in it, giving it more will just burn it. You need to put your plant under your lighting setup and leave it alone. It'll be quite awhile before it needs anything from you. Only when you can lift the container and it feels as if you just loaded it with fresh dry soil, do you give it more water. I mean let it get almost DEAD dry before you give it water again and when you do, make sure you've got it in the correct pH range for a soil grow...6.3 to 6.7. When you do water it, saturate the entire container making sure you get all around the edges...watering very slowly so your water doesn't just run through the soil. You'll only need to give it water the next couple of times depending on how fast it picks back up and starts growing again. I think you could up your knowledge base on the "how to" part of growing and tending these plants indoor if you go to the new grower threads on the forum and read the "Sticky's" there. Most new growers drown their plants because they didn't bother to read up on how to take care of them after you get one going. So the more you know, the better your grow will be.

 

Hi charlie. I grow coco too. I av dun siol for over 6 yrs but totally different to coco . Coco has zero nutes .. like ya said. I ph mine to same as you too or at 5.6 to 5.7 on odd accassion to make sure cal and mag getting through ok. Up to yet i ant ad no spots due to mag deficievies so far.. i think u doin good . I do same and use a quater then half nutes at a mnth. I used canna range. A and b cannizyme and ryztonic etc.
Ya did right to transplant as need cooco in pot to feed em !
Anyway looking good.
sometimes calmag may be needed wi coco. I ant used it yet as my water ppm high but use if get deficiency or lower ya ph once or trace a week to prevent it.
Good luck xxx