the mix does have those little water holder ball thingys (the name escapes me right now) so it could be that even though it feels dry to me,
Just some thoughts here:
You said you were watering every two days. If you are soaking them to runoff that is probably too often, in my conditions and experience it takes 4-5 days with a pot and plant that size. And those thingies you refer to I assume are "water holding crystals" or "hydrogel" which soaks up water into beads then releases it. That may be throwing off your meter somehow, I don't trust meters anyway.
The hyrdrogel is normally not needed nor recomended for inside growing. Outside in beds and pots it's often helpful to reduce the ammt of watering needed during dry spells and prevent moisture stress on plants. Inside we don't have that problem and the crystals can cause a lot of problems (soul gnats & other insects, mold, fungi,and other things that are not always beneficial.
On the other hand if your soil IS actually dry in two days you might have a problem with heat and/or low RH and/or too much airflow. A leaf in pic 3 looks heat/lamp burned, but that might not be it, just kinda looks like is. Another thing to keep in mind is that if your actually drying out in 2 days you are going to end up with nute (salt) buildup in the soil eventually. Too much water is evaporating from the soil, the plant is not using that much, and the evaporated water leaves behind the nutes and they build up.
Finally you can overwater and have heat issues going on at the same time, and have some salts building up.
Anyway just some things to consider.
