Never. As long as the light is far enough away and the temps are all dialled in … All good. Although there is nothing wrong with how you do it!!! I find I get much better veg growth using HPS (others may disagree) which puts me in a great position when I see pre-flowers , as I bump it up to 400w and watch those bud sites grow! My HPS is dual spectrum, so it's great for veg & flower.
Temp is 77 humidisity is 44 going to switch bulbs ow i have smaller ones in there with it so was worried if bulb colored mattered to them
Course it will mate - I have 3 all at different life stages at the moment! They have only known HPS from Birth and they are all thriving mate!
Nice thought would make difference i ran metal halide bulb in my hps so now have to put in the red orange specteum bulb i guess
just put the sodium lamp on ,,,they will all be fine ,,no worries mate ,,,they are all autos so it doesnt matter ,,mac,
One thing to be aware of mate - I am not sure how your grow room is set up regarding extraction etc.. But when you change to HPS - What wattage will you be using because it will bump up the temperature by a few degrees (minimum) !!!! So if your at 77 (25 degrees) now using MH, you need to then make sure your extraction is powerful enough to remove the extra heat, which will be generated from the HPS! Keep those temps dialled in. (example - When I bump up my HPS from 250 to 400w - It adds around 5 degrees to my grow room)
Ok, temperature in VEG can be a little higher! I would say anything in the range of 75 - 84 is fine (24 - 28 degrees) with humidity between 50 - 60%. in flower best to reduce the heat a little 70 - 80 (21 - 26 degrees) with humidity a little lower 40 - 50%! BUT don't worry if you cant achieve that! Sometimes in VEG my humidity is as low as 30%!!!! Bottom line is as long as the temp never falls below 20 degrees or over 29 degrees - Your plant will be happy and comfortable and grow steadily!