Culture indoor

to solve heat issues you would want better venting/fresh air exchange/ more air flow. plants like temps between 75 to 85 any higher than 85 will give you small yields and airy buds, if you can not fix the heat before flower that is, you can also use kelp for heat stress, as well as silica, both do a good job, your roots though is where it matters, you want to keep the roots cooler if you can, if not then you will have to solve heat issues in the grow space, air/fresh air/ more fans, air circulation is important. when you have heat issues during veg it can slow down the growth and if you have heat issues in flower smaller yields ect.

Forgot to mention that good 100W led should be enough all the way through veg with two plants. Or 250 HPS or something but the m,ain point is you don't need to use so much power during seedling stage 'cos the plants cant take it and you are just raising the light and heating your home

If you are using 600W HPS lamp all the way through then I think money aint the issue here 'cos you are waisting a lot of energy with that lamp and it is only needed during late vegetative/flowering. (If it is HPS) Absolutely best way to deal with heat of 30 degrees is to invest in CO2 system. It is pricey but once you have it your plants will grow much healthier. You will need CO2 meter and controller, CO2 bottle and regulator with solenoid valve attached to it. When you have all this you can set your tents ambient CO2 level to 1500PPM and by doing this the plants optimum photosynthesize temperature will rise from ~25C->~30C and the plants will start to photosynthesize 4xmore I! http://fluence.science/wp-content/uploads/2016/09/High-PPFD-Cultivation-Guide-9.27.16.pdf If you don't want to do CO2 then probably best way is to get cool tube for your lamp and run air through the tent with additional exhaust fan and IF possible take the venting air from outside when temperatures are lower than inside. Or you could buy movable AC

hi man, what kind of light is it? best and safest way to adjust it is to look up what the light producer is recommending.

At 600 watts and such small seedlings, I would go 60 - 70 cm with a spreader, without a spreader 80 - 90 cm ;-)