Interference from large ballasts.

I designed a Cannabis Indoors controller some time ago, it works great generally but I'm having problems sometimes the Arduino would freeze and I have to reset it to start working properly again. After many headaches trying to debug the program I realized that the freezes happened when the relays for switching on the ballasts kicks in. I'm using a 8 channel relay board to switch loads ( pumps, fans, etc ) ( picture: http://ecx.images-amazon.com/images/I/61OeQRy5c9L._SL1000_.jpg) and I use the same board to switch bigger rating RELAYS ( picture http://ecx.images-amazon.com/images/I/51peTy3gfBL._SL1500_.jpg ) where I have connected the ballasts for the lights, its a pretty heavy load consisting of 24 600W growing lights. I'm using three of those bigger relays, each one controls 8 ballasts.
Sometimes ( but not always ) when there is a change in the relays the LCD freezes but the controller still works ( I got around that by doing a reset on the LCD after each relay switch ) but occasionally ( not very often maybe once a week ) it will freeze the Arduino and that's really not good for the little babies.
I don't have much experience working with loads of this magnitude and I'm a bit at a loss on how to debug this, I tried with a voltage surge supressor connected at the power supply of the Arduino but didn't help, I'd greatly appreciate some guidelines about how to be able to pinpoint the problem. At this point I'm not sure if the interference is magnetic from the coils of the relays or if it is surges that travel trough the wires from the electronic ballasts. I heard from friends that are in the same industry that sometimes the ballasts will make the modems providing internet go crazy.
I'm just looking for some advice from someone with more experience than me in power electronics to suggest what to look for or how to pinpoint the problem.
Thanks a lot in advance.