Ok, They look overwatered first of all.

I think that you ought to invest in some CFL's. The hps is the wrong color of light for vegging. It can be done, but it's not going to be very quick that for sure.

The CFL's will put out similar Lumens per watt as the HPS but the correct color. Plus they are cheap as hell. Not sure if they are available in costa rica though. they are on right next to regular light bulbs here in the states everywhere. So look into it for better growth.

I'll keep following along.