Leakey fittings.......

What would be the best solution for fixing leaky fittings? I tightened the shit out of them (maybe too much???) and they still leak. to be more specific on what is leaking; its the hex nipples between the valves. I was thinking of JB Welding the bastards, but maybe someone else has a better solution. To make things worse is that my valves are already mounted, and I'm using compression fittings so it wakes it really hard to take them all apart. Buy any help would be nice.

Thanks.