Marijuana grow room HPS400 question

A question from a fellow grower:

I have managed to grow with a U shaped scrog and a
80watts HPS hanging in the middle(no reflector). No ventilation and the
temperature is 30oC. But, for 2 hours/day I switch on the 400watts HPS
and the temps climp to 42.My question to you is,
for how long can my plants benefit from the 400w HPS without experience
heat stress? that is, untill i upgrade my ventilation system, do you
think I should use the 400w HPS at all? (my last grow was on 7 hours
80watts/5 hours 400watts and it turned out airy and foxtailed)

I think you should fill out a support ticket. This will allow us to give you a more informed answer

Fill out a "Support Ticket".

I also believe that your airy buds could be attributable to a couple issues. Using an 80 watt lamp, 2. weak nutrient program. However; Until you fill out a support ticket, this is nothing more than an educated guess/s

The customer mailed me a filled out support ticket, so here it is:

Strain; White Widow from clones (which I produced from seed)

Soil in pots,

System type? (what?)

PH of runoff or solution in reservoir? the only ph measurment I do is in soil and turns out 7,5 (although cheap ph meter)

What is strength of nutrient mix? EC, or TDS; This is what I do:I
mix 2,5ml of CANNA PK13/14 and a teaspoon of organic fertillizer (from
see weed. it is described as the mother of all fertilizers!!
N,P,K,Fe,Zn,B,I,Br,Cu,Ni,Mo,Co,So,Si,Al and many many other things!) in 5 lit of water. I apply this once a week. I usually water every 2-3 days.

Indoor; closet 1,20mX60cmX30cm

Light system, size? 80 watts HPS in the middle of U-shaped scrog,
2X20watts clf at each end of the U-scrog, 400watts HPS on top of
everything (but only for a couple of hours)

Temps; Day 30-38oC, Night ~20

Humidity; Day, Night N/A

Ventilation system; Yes, two brushless fans 10cm blowing air out and a 10inch bathroom ventilator also blowing out

AC, Humidifier, De-humidifier; NO

Co2; NoOne thing to point here is that i was
pretty happy with my grow before installing the 400HPS and fans. I know
it wasn’t the bigest possible grow but it was running even cheaper than
the standard 400/600watts setup.

So, my only
question is about how long can my girls tolerate 38-40oC without
suffering heat stress so that I can boost my yield a bit.