Help with humidity

Im currently on week of in flower and my temps in the day are around 75F and 55-60% humidity. Night time temps get to 70F but the humidity goes to 65%. I have a 440cfm exhaust fan with a 2x4 tent and 400w hps. Do I need a dehumidifier ? If so, what size or kind do I get ?

Yes a dehumidifier will bring RH down to maybe yield more, and more resinous bud, but it will raise temps, so its a balancing act.

For years I never adjusted RH, but I am now. You don't need one, but it might help if you have space, and it doesn't heat you up too much. I paid $187 for a Keystone model KSTAD70B at home depot and it pulls 2 gallons per day out of my room, bringing RH from high 60s to high 30s. It feels great in there, and the plants seem to love it.
The water is used in the grow room, or out in the yard.

I use it because my basement is damp during summer. I'm not convinced low RH increases quantity or potency, as is commonly believed. So many sticky strains come from equatorial environments where its plenty humid.

if you have good circulation and if it isn't packed too tightly together in your tent you might not absolutely need one, but it would definitely help

Good

I just ran a pretty dense indica w temps 70-85, rh 65-50. No problems but I had only 4 plants, 6" 500cfm exhaust, 2 circulation fans.

I did try a mini dehumidifier but i think the air exchange messed it up. It only pulled like 1cup of water a day n didnt really drop rh in tent.