Sealed grow room help.

whats your lighting situation that's a big grow space. I would assume ph and ppms are under control as you have larger plants that grew without deficiencies

 

I would take it out then until you get a co2 reader, I assumed you had that calculated. those plants are definitely not liking something, if the issue only started after the co2 was added I would get it out yesterday. kind of confusing tho because co2 is heavier than oxygen so to me the plants lower should be showing more signs than the taller ones up higher is the co2 closer to the taller one I am intrigued lol

 

but a heads up especially not in a closed grow tent you have 100 sqft of grow space that's like 3,000 watts for a minimum suggested watt per sqft of 30watts. I know lights hitting them however I would imagine a lot is escaping. those take up maybe 7 to ten ft of grow space? you may not have an issue just keep that in mind if towards flower they don't start producing like they should. I haven't seen a HLG 500 I know the 550's are almost 900$ 500 watts

 

How many PPMs of CO2 are you running? How close are your lights to the plants? Where are you measuring your RH?

 

When you add co2 you have to also add more nutes and more light. Get your temps up to the mid 80s, humidity in the low/mid 60s and match your nute ppms with your co2 ppms (1000ppm of nutes and CO2 would be ideal for your plants at this stage of growth.)

Your LEDs have more usable spectrum than an HPS so less is wasted via heat which means you can run hotter room temps without burning the plants.

Adding CO2 allows you to push everything harder. Higher temps increase the plants metabolism which means accelerated photosynthesis which means more growth! The humidity is increased to get in the ideal VPD range 0.8-1.1kPa. 85F and 64% RH gets you right around 1.1kPa. Dial those in and your plants will bounce back almost immediately.