Low Light Solution

Lets forget about exact recommendations of product for a second. Based on the post I am thinking you have minimal lighting experience.

Regarding the lens, you do not need a 2.8, it will give you more light shooting at 2.8 or wider but then you also have to watch for getting focus nailed because the shallow depth of field. F4 - F5.6 is a very common range to live in for portraiture especially if there are 2 people in the frame you will want the extra depth of field. I'm not saying a faster lens isn't a good idea to have but definitely not the primary problem your having. I personally have a 50mm 1.4 and an 85mm 1.8 and i usually do most portraits about f4, unless I really want to get soft bokeh when I am out shooting in a street or at park, and then i will open it up to 1.8.

Now your using LEDs, personally LEDs are quite under powered compared to a good studio strobe which should be rated 200-300 watts, or even a good speedlight which is probably 60-100 watts. So while the low power is a bit of a fight, you should be able to mitigate that a bit by using a higher ISO. On the plus side, the lighting is constant so you should be able to see what results your getting without a camera. These LEDs are primarily built for video such as vlogging, and you can see they add plenty of light if they are very near the subject. So one problem I see is that you may be shooting with the lights too far away from the subject so they are not providing the lighting you need.

Secondly I see you placed the two 30w lights behind the subject and 15w lights in front... you will get better results swapping that around. Back-lighting can be done i studio with 1 light or none even, I usually use a diffuser/reflector panel to bounce some light on the backdrop if I need to. Put the 30w lights and you should see the difference right away. In fact I would recommend going to 2 forward lights and forgetting any in the background for now, your camera may have been exposing for the background and making the situation worse as the foreground would be under exposed. Its hard to know what exactly happened without details and example images. Once you can master lighting the subject then you can add more lighting to the environment.

Even with 30w, it will require you be close to the subject with your light. Even if you had a high power studio strobe, the closer you can get the lights to the subject the softer the light will be, conversely setting the stand up 8 feet away is going to produce heavy shadows somewhere even if the light produces enough power to light from that far away. This is very contradictory to how many people see lighting when they start, (hard light is created the further away, not the closer to the subject) This is why the sun is not great in the middle of the day for photography.

I highly recommend reading up and watching some tutorials on lighting, angle to the subject, proximity of light to subject, power of each light lighting location all make for very distinct differences in lighting. I would work on getting good results with 1 or 2 light sources, getting good even lighting and then mastering Rembrandt lighting will cover 90% of what you need, from there you can find ways to add additional lighting for effect.

I come from a school of thought for lighting that is much like David Hobby, he wrote a blog call Strobist back in 2006 which you can easily searched for via google. His gear, like mine, are speedlights and triggers, but I think its a good thing to read over for technique as well even if your gear is completely different, as it will peek behind the curtain on how you can create interesting lighting in and out of studio with very simple techniques. Gear changes, lighting techniques do not.

At the end of the day you have something portable but not super powerful, so I would master it and play to its strengths and you will evolve ideas on what sort of gear upgrades you will want in the future.