well... thats just yumas. They are really weird like that. I can't offer up any real help other than they are just it or miss. I've had yumas directly under 250W MH lighting and other have melted 25" below 150W m lighting. They are just weird. I can tell you though, the more red coloration that they have, the deeper the water that they came from (usually). So... I would just try to keep them totally shaded if they are going to be under MH lighting. Or, just do what a lot of LFS do and just have a tank set-up with low PC or T5 lighting and have it just set-up for Ricordea. Good luck.