If you can exhaust outside that area or just to the outside, that can help. But if ambient RH is already high in your region, that won't help much either.
bigger dehum needed if that cannot do it, or fewer plants. once they get big and all transpiring alot, you get a lot of water vapor released.
40-60 is fine. you probablywant it under 60, but if temps are also high it can be helpful. Resulting VPD dictates how fast the plant drinks which relates to the rate of vapor the plant releases. lowering temps could help reduce RH caused by plant, in this context, too.
Because of RH issues i only grow at certain times of the year. When my furnace is on, my ambient RH inside house is ver low. So i can control the RH later on with larger plants. I still need a dehum even though ambient is 25-30 % if nothing is growing in the house.