PH Problem?

Yeah, it could be pH. The pH should be between 6.2-6.8 for soil. You might have to get some pH up from a hydro, garden or pet store.

 

I agree with smokin

However, you need to test the pH of the solution you give your plants, i.e., the nutrients and water together. If your tap water pH is 8.0...you normally don't have a problem when grow big (I'm guessing fox farm) is added, as the pH of the grow big is low. I've tested the pH of my tap water...also pH roughly 8...and it is right about mid 6's with grow big added.
Your plants look like early propagations/seeds...thus the problem is not likely to be an actual nutrient deficiency in the soil (what soil are you using?).
Plants always exhibit a nute deficiency when there is a pH lockup.
My recommendation? Go to a pet store...buy an aquarium pH tester (you should not pay much more or less than $10) and balancer kit (follow the directions on the bottle closely, try and adjust the pH to around 6.3-6.5)...and give your newly propagated plants/seedlings nothing but straight water until your plant develops a new set of leaves that doesn't exhibit this problem.
If you're using fox farm soil, miracle grow or any medium with an added fertilizer...use only the pH adjusted water (straight water with pH down added )schedule for the first 30 days.

 

2 things to add.

Firstly, watch the guys face in the hydro store when you ask for pH Up. They don't get much call for it.

Secondly be wary of aquarium pH balance kits, they tend to balance the water to a safe range for fish (between 6.8 and 7.8), and include various chemicals to condition the water for fish, helping them produce a 'slime coat' to protect from disease. Most of them do not allow you to set your pH exactly where you want it. Have a good read of the package before parting with your hard earned.

On a related note, aquarium stores also sell a tapwater conditioner which is supposed to lock up all the chlorine and heavy metals within minutes. I have 1 seeder that's getting watered straight from the tap (no standing time) with this product. No conclusions as yet.

/edit: Conclusion: It died. I think the conditioner produced a slime coat on the roots so they couldn't take up any nutes. Worth a go I suppose.