If it hasn't been stated yet, GFCI's detect fault to ground, not overload. A GFCI is a safety device, not over current protection. While a GFCI is *rated* at 15 or 20 amps, this is a different rating.
If GFCI's are installed in your kitchen, bath, garage etc... for safety's sake, don't remove them, these devices are there to protect you.
The circuit breaker in the panel is over-current (too much amperage) protection, and since you described that your lights will trip breaker as well as GFCI devices, a fault to ground could cause fault on either/both. The ground is a path to clear a fault (tell system something is wrong and trip breaker) rather than involve US in the path to fault (BAD).
I'll come right over and check it out

(if it was only that easy...)
At all costs, be safe!
IMO opinion, every grow room should have it's lights/equipment plugged into a GFCI. If the GFCI trips, the equipment may be faulty.