The fact BOTH transmissions were equally low implies the prior check might not have been correct.
Most all transmissions are checked running. It is also often best done when cold, despite manufacturer instructions in some cases, as "splash" from usage can skew the reading on a dipstick (IDK your particular set-up, this is a generalization).
1/2 qt. of leakage from each would be a virtual toxic spill, not stains on a drip pad. Something isn't quite adding up here...
Lubegard Red is an excellent and truly effective transmission additive. It contains synthetic esterified oil base which functions extremely well as a seal swell agent. It also reduces temperatures slightly (about 5F in my case; not huge), in addition to the anti-wear additives it contains. I am not familiar with the product RTF linked; it may be equally effective so I am not advocating this over that.
Their "blue" engine additive is also highly effective in both absolute and cost terms, and true whether gas or diesel. 1oz/qt of lube is adequate.
LUBEGARD Automatic Transmission Fluid Protectant