Yep, you have low RH for the veg stage.. not only for your temps.
That post is right about VPD btw the common approach is 90% RH for seedling, 60/70% for veg, 40/50% for flowering.
Keeping RH low during flowering allows more resins and thricomes production[ coz they are a natural response to low RH ], avoid mold and other issues.
The higher RH you can have without problem, the better... in any stage. [I used to have a lot of condense during seedling even inside my air extractor... and this is not the safest thing for your indoor room... but they surely thrive a lot better]
The more you keep the light on, the more the RH is going to decrease without a proper humidifier.
Well, that explains why I've always had issues over the years with veg and especially late in veg. I never gave it much thought because when I switch to flower the plants really perk up. Fortunately, veg is coming to an end for this crop. I have an end date for this season (due to personal obligations) and to achieve it I'll be flipping to 12/12 in two days. It looks like the girls have grown a few inches since being under the qb's. Not bad considering that I simultaneously cooked and froze them for the first 5 days with the leds. They should be 15 -18 inches tall by the flip so I'm ok with it.