What are you adjusting the pH of it with? What water source are you using?
Even tho that seems a bit warm for beneath a T5 (it is summer after all), still not quite warm enough that heat would have any negative effect. Plus, inside of the dome with the lights on seems like it would even have been a bit warmer (due to the greenhouse effect).
Unless your water is shit, you used way too much pH adjuster, or you forgot about how you gave them something else (people often do, conveniently, or often it was just a 'little bit' of something that turned out to be a lot)... then the culprit more likely lies with the potting soil. Ocean Forest has a lot of nutrients (guano, fish emulsion, meals) in it already, and even though it is an all natural\organic mix these things can still burn very young plants.
Some people are going to tell you they have started seeds in OF and they did fine. Other people are going to say that OF burned their seedlings or very young clones. They are both probably right to some extent; batches of bagged soil might be inconsistent and, of course, strains are highly variable. I personally use SAM#4 for seedlings and clones, whenever possible (Happy Frog is fine), SAM#4 mixed with Ocean Forest for older plants (I amend this further).
Keep an eye on them. Water properly (when the cups are light), watering more isn't going to help any. However, misting the leaves periodically might help ease the nutrient burn. In this case, higher humidity could actually help, but still not over 70% RH.