SDL_SetRenderDrawColor transparency artifacts, and miss coloring

I’ve ported my very simple GDI sprite renderer (written in C++) to SDL, but i cant seem to get the colors right.
And transparency has some strange artifacts.

I’m getting my colors from a buffer of custom color classes, and since i have made my own custom transparency, using 255 as the alpha value everywhere.

this is my drawing code:
SDL_SetRenderDrawColor(_renderer, _buffer_0->get(x, y).R, _buffer_0->get(x, y).G, _buffer_0->get(x, y).B, SDL_ALPHA_OPAQUE);
SDL_RenderDrawPoint(_renderer, i + (_scale_factor * x), j + (_scale_factor * y));

Edit: sorry, i couldnt get the code indented blocks to work
also, if needed i can post all the code, but it’s a bit much

I fixed the colors, however some parts of the plane are still transparent, but i think it isnt SDL related

Edit: i fixed, had no relation to SDL, just to my color class, which was used a bit differently to the GDI one, therefore the issues

Are there any obvious points of failure here?