I'm not very educated on growing very much but I use soil currently no nutes I'm going out tomorrow to buy some (if you have any suggestions...) I have a ph meter and measure my water at around 6-6.7 ph level temp 78-88 F humidity runs around 55%. My light is a VIPARSPECTRA 300w LED (I know it's not the bestest of lights but it's just a starter). I dont know if this matters much but it's in a 3 gallon pot. I hope this helps.
could you expand on what you think it may be?
I agree that the plant generally looks healthy and the yellowing only affects the first couple sets of true leaves that can be expected to die off eventually, similarly to the cotyledons.The plant looks healthy in my opinion and leaves do die and turn different colors over time. This looks like one of the baby leaves so I really wouldnt worry, like I mentioned they look healthy. Most people freak out and start to add all types of things and could easily make it worse
Your plant looks perfectly healthy to me. Those yellowing leaves just look like they are in full shade. They should just almost fall off when you touch them and than you can forget they were ever there. As a coco grower I will leave the feeding advise for someone with more experience than I.