try a lower vpd.. working wonders for me so far... some plants can grow well in anything, but others need a little more coddling relative to temps and RH. My dehum goes +3% to -3% of target, so i have a 6% swing over time. I let it tip over 60% then drawn back down to 55-57%. 26-27C being the peak. I was shooting for 1.2-1,3 (atmospheric not 'at leaf') and got way better results than ~1.5 or higher, which you are around ~1.8.
some plants may do okay in that, but you'll have better consistency if the VPD is lower. If your heart is set on co2, may need to adjust this a bit. think you operate at a bit higher temps to take full advantage of co2. from what i understand it's not cost effective, meaning you'll have a better return from adding sq footage than supplementing co2. unless space is capped, just adding a new tent will be financially smarter. Plus, no risk of killing yourself with co2.