Please help me on diagnosing plant problem?

Hi everyone.

Can you help me looking at my plant and see what the problem could be.

It started growing great with perfect green leafs but then the bottom leafs started curling down and now they are loosing color. The top leafs are slowly getting green.

Here is are pics of before and after.

looks ok, any other info, what type of soi, feed, temp, hum, ph, ppm, etc..

So you dont think there is any problem from the pic under the sun. Ill get the info you ask for. The fact that the green leaves are turning yellow worries me.

looks normal to me, new growth comes out light a darken green. Bottom leaves lighten up yellow and fall off over time.