I started this grow with 2x2x4 with a 350 watt LED...

This will depend on a couple things , firstly I can see that your day time temps are pretty high so adding another light in your room may not be a good idea it may raise the temps higher and at 29C that's already pushing the limits . However if you can get the temps to be lower I wouldn't see a problem with adding another light . Being that they are in flower you want as much light as you can get more light = bigger flowers = more yield . The only thing that would worry me here is that if you add that other light you will go above 30C in that tent and then your plants will essentially shut down during the day because its too hot. Your ideal temp ranges for flower should be 26c during the day and 18c at night , if you cant reach those temps the closer the better . If you think that your other LED panel won't add a lot of heat try it out , but watch your temps you dont wanna cause heat stresses at this point . If it works out were the temps stay the same for you but you get more light keep it in the room if you see that the temps are too high and hard to control take it out or get a stronger exhaust fan for your room . I hope this information helps you understand that you can use more light always but you have to pay attention to the risks that come with it ( high temps , heat stresses , C02 problems ) -Happy Growing!

Hey TNB, yeah it's totally worth it , it will increase the PAR and the LUX and the plant will reward you for it with a bigger yield and a quicker flowering time. Hope this helps ! 🚀