3 week old plant problems

Hello,

I'm about 3 weeks into my first grow and the little ones dont seem to be doing too good! They are quite small and initially stretched under a T5 fluorescent light but after I moved the light down they stopped. They are growing in houseplant compost I picked up from the local garden centre, it is a reduced peat compost with added lime and vermiculite and the label tells me it contains enough food for 4 weeks.
They are now under a 400W HPS bulb about 24" away. I water them with about 10ml of reverse osmosis water everyday (soil seems to dry out very quickly) with about 0.5 ml of Bio-Grow 8-2-6 fert per litre. This is my first grow and have not yet acquired a ph meter and i have no idea what the temperature exactly is but I'd reckon its between 20 and 25 C. Seeds are dutch passion blueberry.
Anyway, the majority of the plants have yellow spots on the leaves and a few have started to curl at the tips. Any ideas as to what could be causing this?

Those plants are too young to be receiving any nutrients, especially if the soil you're using already has nutes mixed in. Also, if you're going to continue to use RO water, then you have to supplement the elements that have been removed by the purification process. Calcium, Magnesium, and Iron are the big three. CalMag+ is highly recommended. That's most likely why you're seeing the spotting, and the burnt/curled leaf tips are probably the result of overfertilizing.

Take care. :jointsmile:

dont look like they get the rite amount of light there way o tall for 3 weeks