You can blame the sun. There's no way we can replicate the power of natural sunlight indoors, we can however give them artificial lighting to make them grow and produce but it by no means matches the power of the sun.
Same thing happened to the few starter plants I could keep growing indoors until this wet spring finally broke and let me get in the dirt. All my tomatoes were gonners but I did manage to get some peppers set out. Most all the leaves burnt up to a crisp. The plants did have enough of a root system that some (not all) suckered out and grew.
Hardening off the plants would help, takeing them outdoors and increasing the time left there daily, would be the sanswer but it's a lot easier said than done when it comes to hydroponic plants.
Best of luck on your future grows and welcome to HG!