First grow - Should I be concerned about my high VPD or keep on rocking?

This is just the ambient VPD, your plant's VPD is lower.The leaf temperature is definitely 2-3 degrees colder.1.3 to 1.4 is the maximum VPD for your plantAbove that, she has trouble breathing.Then it happens that it suffers from over-fertilization.Because the plant is forced to absorb more nutrients due to the high VPD.

The good thing is your leaf temps are a few degrees (F) lower than atmosphere, so it's a bit lower than what you calculated. IT's still too high, and it absolutely will negatively impact rate of growth if it continues. Mold risk isn't a problem until above 65%, so you have room. Allow the humidity to go higher. All is well. A slightly high 1.5 vpd isn't great but in my experience still allows decent growth. For reference, my familiarity is based on atmospheric temperature readings, because that's how the probe providing the information works. Try to stay below 1.5-1.6. If it spikes "1" day i wouldn't worry too much about it. I recently had a humidifier wick go bad and it took 10 days for the replacement. My VPD shot up to 1.8-2.0 and my growth virtually stopped during that time... it was incredibly slow and noticeably different than before. Once i got a humidifier running again it was picking up the pace within a few days. High VPD wil increase transpiration. If plants are taking in more water per day than normal, you may need to draw back your fertilizer concentration a bit. Keep an eye on that. Let the plant show something before assuming anything. high temps and/or low rh also increases evaporation. probably not ideal for trichomes, either.

Honestly, yeah that VPD is a problem in general. You can dig into the science more yourself but the girls need a certain VPD range to do things properly. Over time you'll run into issues. RH itself is misleading but still tells a story here, you would be well served to try to gain some points on that IMO. VPD being out of range is like pH being out of range, you simply lose things in a discrete manner until it is fixed. The mold growth potential is a lot more advanced than RH although you're generally fine under 60% with good airflow, cultivar depending. At 40% RH, if you aren't controlling more advanced metrics (which no-one outside of a lab is) I would expect your buds to be losing some of their final weight potential as active water is ripped away. New research here is also showing if you are using a traditional AC or dehumidifier to control the RH or temperature, then you're demolishing trichome heads in the process...presumed mechanism right now is local scale VP delta/gradients (caused by compressor cycles in these machines). In other words, 40% RH driven by a machine is like way worse than 40% ambient. I agree you can push the boundaries of VPD in late flower. To me a VPD greater than 1.4 is pushing it, 1.7 is about as high as I let mine go.

Id just make sure your humidity doesn’t get high like don’t use a humidifier Most of the time if you put the exhaust fan on a high setting and the grow light being on high is normally enough to keep the humidity down low enough Unless you live somewhere extra humid I doubt u will need a dehumidifier during flower. Honestly don’t stress it to much just make to keeps below 84degrees Plants are very hardy durring late flower they can handle pretty much anything you throw at them