Yes, you can have too much light (and heat can be a limiting factor in smaller spaces too), they can only use so much. I have experimented with hanging heights at different heights the last 3 grows with MH LEDs and have found that 20-22" above the canopy is ideal in the vegetative state (best balance of coverage and intensity). If they are put closer earlier in veg they can stress the plants, and if they are hung at closer ranges like 16" later in veg the plants become almost too compact and bushy with very tight internodes. I have being using the SCROG method, so the canopy has been quite uniform throughout the grow and track what heights the plants seem to respond to best, while producing the best results.
For flowering, I find that the ideal height is 14-16" above the canopy. When I tried 12" last round, I got some light bleaching on the tips right under the lights. I should also state that these optimal heights are for my grow space and conditions and can vary with different temperatures, growing methods, nutrient strength, strain, etc.
I like a little more light per square foot, last round I was at 80W per square foot for my SCROG canopy....I was able to pull this off due to being in a bit of a larger room vs a tent, 5 lights for optimum and even coverage (three MarsII 900's, and two Reflector 48's to cover dimmer spots on the screen), and with really good ventilation. The difference was definitely noticeable in the results.....bud density, bud size, trichome production was all way up compared to previous grows where I was at 60W/sqft. I also find that with the MarsII 900 that the optimal coverage at my hanging heights is more like 3'x3' (for flowering) rather than the recommended 3.5' x 3.5' listed on the website. YMMV
I also got another great news:the container which under custom clearance will arrive at our warehouse today
We got this news within 1 hour.
You did a good experiment there,you have found the ideal distance and method in growing for your own.
Wish everyone a nice weekend.
