Hi Karen,
I would suspect it was the higher temps too that the little plecos weren't used to. I would venture to say that most bristlenose are kept and spawned/raised in temps of around 78-80. At 1", they are about 8 weeks old and still a bit fragile. You might want to consider getting a terra cotta pleco tube and tying the short variety of java fern to the top to cover the top. Makes an awesome cave for them! And can easily be moved while cleaning the tank.