Strange Yellow, rusty almost colour on new leaves, anyone help?

Hello there

Originally twelve plants from poor cuttings, now seven. originally simply under flourescent 80w and then transferred to a makeshift 200w sodium. Basic fertiliser for ordinary house plants and good soil.

Have no ph kit, no idea what the humidty is, and have only just transferred to UFO 50w light and safe, clean environment. Plants have recovered from their shocking abuse and are now growing hapily but in the last day have discovered the leaves, new leaves, towards the top of the plants turning a yellow almost rust colour. Anyone have any ideas. have posted some fuzzy photos as a rough guide.

thanks